Source : WordNet®

thunk
     n : a dull hollow sound; "the basketball made a thunk as it hit
         the rim"

Source : Free On-Line Dictionary of Computing

thunk
     
         /thuhnk/ 1. "A piece of coding which provides an
        address", according to P. Z. Ingerman, who invented thunks in
        1961 as a way of binding {actual parameters} to their formal
        definitions in {ALGOL 60} {procedure} calls.  If a procedure
        is called with an expression in the place of a {formal
        parameter}, the compiler generates a thunk which computes the
        expression and leaves the address of the result in some
        standard location.
     
        2. The term was later generalised to mean an expression,
        frozen together with its {environment} (variable values), for
        later evaluation if and when needed (similar to a
        "{closure}").  The process of unfreezing these thunks is
        called "forcing".
     
        3. A {stubroutine}, in an {overlay} programming environment,
        that loads and jumps to the correct overlay.
     
        Compare {trampoline}.
     
        There are a couple of onomatopoeic myths circulating about the
        origin of this term.  The most common is that it is the sound
        made by data hitting the {stack}; another holds that the sound
        is that of the data hitting an {accumulator}.  Yet another
        suggests that it is the sound of the expression being unfrozen
        at argument-evaluation time.  In fact, according to the
        inventors, it was coined after they realised (in the wee hours
        after hours of discussion) that the type of an argument in
        {ALGOL 60} could be figured out in advance with a little
        {compile-time} thought, simplifying the evaluation machinery.
        In other words, it had "already been thought of"; thus it was
        christened a "thunk", which is "the past tense of "think" at
        two in the morning".
     
        4. ({Microsoft Windows} programming) {universal thunk},
        {generic thunk}, {flat thunk}.
     
        [{Jargon File}]
     
        (1997-10-11)