A dull, hollow sound: the thunk of a metal pipe striking a tree.
To make a dull, hollow sound: "Her hard shoes thunk on the stairs” ( Carolyn Chute).
Nonstandard A past tense and a past participle of think.
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.