noun

• (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."

verb

• (computing, transitive) To intercept and modify calls to (an API), usually for compatibility purposes.

noun

• (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."
• (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.""

noun

• (uncountable, microscopy) Abbreviation of scanning helium ion microscope.