To require too little work from; to work insufficiently.
2
Obsolete To work or operate in secret or clandestinely.
[H]e raiſeth (in priuate) a nevv Inſtrument, one Sertorius Macro, and by him vndervvorketh, diſcouers the others Coũſells [i.e., counsels], his Means, his Ends, […]1605, Ben[jamin] Jonson, “The Argument”, in Seianus His Fall, London: […] G[eorge] Elld, for Thomas Thorpe, →OCLC, , signature [A4], recto:
3
Ambitransitive To do less work than necessary (on).
to underwork a painting
4
To do work for inadequate payment.
5
To injure by working secretly; to destroy or overthrow by clandestine measure; to undermine.
But thou from loving England art so far, That thou hast underwrought his lawful king.c. 1596 (date written), William Shakespeare, “The Life and Death of King Iohn”, in Mr. William Shakespeares Comedies, Histories, & Tragedies […] (First Folio), London: […] Isaac Iaggard, and Ed[ward] Blount, published 1623, →OCLC, [Act II, scene i]:
6
To do similar work for a lesser price than; to undercut.