verb

• (humorous, nonstandard) past participle of think
  "Who would have thunk those guys would have a problem with a little lie?"

noun

• (computing, functional programming) A delayed computation.
  "Not surprisingly, a thunk is more expensive to store than a single number[…]."
• (computing) In the Scheme programming language, a function or procedure taking no arguments.
• (computing) A specialized subroutine that one software module uses to execute code in another module.
  "If the provider of these DLLs has not updated the code to a 32-bit environment, you will have to switch to a new 32-bit library or write thunks between your 32-bit code and the 16-bit DLL."

verb

• (computing, functional programming, transitive) To delay (a computation).
  "Not surprisingly, a thunk is more expensive to store than a single number, and the more complex the thunked expression, the more space it needs. For something cheap such as arithmetic, thunking an expression is more computationally expensive than calculating it immediately."
• (computing, transitive) To execute (code) by means of a thunk.
  "This efficiency is offset by the fact that some of the calls made by Win32 apps must now be thunked down to 16 bits, something that isn't necessary in Windows NT and OS/2."