shim

Etymology 1

Unknown; from Kent. Originally a piece of iron attached to a plow; sense of “thin piece of wood” from 1723, sense of “thin piece of material used for alignment or support” from 1860.

noun

1. A wedge.
2. A thin piece of material, sometimes tapered, used for alignment or support.
   The second adjustment [to a door that keeps swinging open] will require the screws to be loosened, and a shim or packing piece pushed behind the hinge to bring it into line. 30 January 2016, Jeff Howell, “Swinging doors: it's not open and shut”, in The Daily Telegraph (Property), page 15
3. (computing) A small library that transparently intercepts and modifies calls to an API, usually for compatibility purposes.
   Shims intercept Win32 API calls from legacy applications, as defined by system administrators, and then modify the call before passing the code to Windows for execution. 2010, Russell Smith, Least Privilege Security for Windows 7, Vista and XP
4. A kind of shallow plow used in tillage to break the ground and clear it of weeds.
5. A small metal device used to pick open a lock.

verb

1. To fit one or more shims to a piece of machinery.
2. To adjust something by using shims.
3. To adjust the homogeneity of a magnetic field, after the mechanical devices once used for the purpose.
4. (computing, transitive) To intercept and modify calls to (an API), usually for compatibility purposes.

Etymology 2

Blend of she + him.

noun

1. (informal, often derogatory) A transsexual person, especially a trans woman; (loosely) a drag queen or transvestite.
   He — or "Shim" (she/him), as film director John Waters called the actor Divine — was as much a paradoxical as a perverse fellow. 1998, The Seneca review, Hobart Student Association
   "We call him shim— short for 'she-him.' May 30 1995, The Advocate, page 11
   Yes Maam, or Sir or just what / how do you address a shim? 26 Jul 2004, 13:56:44, grdog, “Wisdom of Great Leaders”, in alt.bitch.pork (Usenet)
2. (informal, often derogatory) A person characterised by both male and female traits, or by ambiguous male-female traits; a hermaphrodite.
   […] that I was a hermaphrodite, and that things would probably be getting much, much worse as other "parts" of me began to grow manly and I made the full transformation into a "shim." 2009, Laurie Notaro, The Idiot Girl and the Flaming Tantrum of Death: Reflections on Revenge, Germophobia, and Laser Hair Removal, Ballantine Books, page 89