thunk definitions

WordNet (r) 3.0 (2005)

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

Merriam Webster's

I. dialect past and past participle of think II. noun Etymology: imitative Date: 1947 a flat hollow sound III. intransitive verb Date: 1949 to produce a flat hollow sound ; make a thunk