wack / whack are similar-sounding terms with different meanings (referred to as homophones). To better understand the differences, see below for definitions, pronunciation guides, and example sentences using each term. 👇
wack: NA
whack: (noun) the sound made by a sharp swift blow. (verb) hit hard.
wack: w·AE·k
whack: w·AE·k
(Examples are Wikipedia snippets under the CC ShareAlike 3.0 license. Definitions drawn from WordNet.)