Figuratively That which causes stress or is extremely difficult, especially that which may cause failure at a task.
That test was a killer.
The final hill in the race course was a killer.
3
Figuratively Something that is so far ahead of its competition that it effectively kills off that competition.
Digital streaming platforms are CD killers.
4
The killer whale.
Archaic or by ellipsis
Theſe Killers are from twenty to thirty Feet long, and have Teeth in both Jaws that lock one within another. They have a Fin, near the middle of their Backs, four or five Foot long. They go in Company by Dozens, and ſet upon a young Whale, and will bait him like ſo many Bull-dogs; ſome will lay hold of his Tail to keep him from threſhing, while others lay hold of his Head, and bite and threſh him, till the poor Creature, being thus heated, lolls out his Tongue, and then ſome of the Killers catch hold of his Lips, and if poſſible of his Tongue; and after they have killed him, they chiefly feed upon the Tongue and Head, but when he begins to putrify, they leave him. This Killer is without doubt the Orca, that Dr Frangius deſcribes in his Treatiſe of Animals.1734, Royal society of London, The Philosophical Transactions and Collections: Abridged and Disposed Under General Heads, Volume 9, Thomas Bennet, …, page 429:
This skull, which has all the appearance of being that of a full-grown animal, is just one quarter the length and breadth of the skull of the adult common Killer (Orca gladiator).1866, Gray, Catalogue of Seals and Whales in the British Museum, Volume 1, page 283:
4 more examples
Fig. 188.—Grampus or Killer, Orca gladiator. (Flower, art. “Mammalia,” ‘Encyclopædia Britannica.’)1891, William Thomas Blanford, Fauna of British India, Including Ceylon and Burma: Mammalia, Taylor & Francis, page 576:
We once saw an attack made by three killers upon a cow whale and her calf, in a lagoon on the coast of California in the spring of 1858.1895, The Royal Natural History, Volume 3, Frederick Warne, page 55:
Few animals known to man possess the savage and murderous nature of the small whale-like animals known as killers or orcas. They pass under various names as black fish, killer, orca, kill fish, sea tiger, and deserve all the titles.1908, Charles Frederick Holder, Big Game at Sea, Outing publishing Company, page 137:
There is, however, one species of whale that habitually preys upon other warm-blooded animals—the killer whale. Really a large dolphin, the killer was classified by Linnaeus as Orcinus orca, and by Cope as Grampus rectipinna.1966, Sarah Regal Riedman, Elton T. Gustafson, Home is the Sea: for Whales, page 116:
5
Figuratively A remarkably impressive person or thing.
The head of the Environmental Protection Agency quakes with mirth at his own punch line. Grimaldi chuckles through his teeth. “A killer, Tom, an absolute killer.”2004, David Mitchell, “Half-Lives: The First Luisa Rey Mystery”, in Cloud Atlas, →ISBN, page 130:
Picture perfect, you don't need no filter / Gorgeous, make 'em drop dead, you're a killer2020, “Intentions”, in Changes, performed by Justin Bieber ft. Quavo:
6
Hobbies, Lifestyle, Sports A knockout form of darts or pool involving several players.
7
A club used for killing fish.
8
Hobbies, Lifestyle, Philately A particularly heavy type of handstamp, or portion of one, often obscuring a large part of the postage stamp.
9
Synonym of virama (“kind of diacritical mark”).
In the course of its adaptation to non-Indo-Aryan languages, the Burmese script has acquired some features that distinguish it from other Indic scripts. The killer, or virama, participates in some common constructions that would be clumsy to handle the way they would be in the other Indic scripts, so the control function of the virama is separated from the diacritic function of the killer. The virama, 0F4D is used to form conjunct consonants, while the killer, 0F52, is a simple diacritic and has no effect on character shaping. The killer is also combined with the VOWEL SIGN O (0F4B) to form the low level tone vowel “o.” When used this way, this symbol is known as hyei hto, or “thrust forward.”1992, Andy Daniels, Joe Becker, “Unicode Technical Report #1 - Burmese, Khmer, and Ethiopia”, in Unicode Consortium:
For example, although the ‘vowel killer’ diacritic may be called a ‘pulli’ in Tamil, it is still referred to by the Unicode character names as a ‘virama’.2002, Richard Ishida, “An Introduction to Indic Scripts”, in W3C:
2 more examples
Thai words that have been borrowed from Sanskrit, Pali and English usually try to retain as much of the original spelling as possible; as this will often produce pronunciations that are impossible or misleading, a ‘killer’ symbol is placed above the redundant consonant to indicate that it may be ignored2002, David Smyth, Thai: An Essential Grammar:
Sometimes the ‘killer’ sign, called kaaran in Thai, cancels out not only the consonant above which it appears, but also the one immediately preceding it.2002, David Smyth, Thai: An Essential Grammar:
It all says that Elephant's Memory is a killer band.1985, Dave Marsh, Fortunate Son: Criticism and Journalism by America's Best-known Rock Writer, Random House, →ISBN, page 224:
This is followed by a recipe for that very killer dish: "Eat and remember this, the greediest of all Popes" is their merry exhortation.2000, Various authors, The tablet, page 798:
“Ahhh, Avery,” shouted the Yurtmeister after a full hour of intense volleyball. “That last serve was absolutely killer.”2009, Amy Bryant, The Great Scavenger Hunt, →ISBN, page 122:
However, there is something very killer about drinking whatever battery acid and paint thinner concoction it is that they make malt liquor out of, in broad daylight, slumped down on the pavement2010, Al Burian, Burn Collector: Collected Stories from One Through Nine, →ISBN: