From the best English dictionary IMHO: https://www.ahdictionary.com/word/search.html?q=wow https://www.ahdictionary.com/word/search.html?q=wow > wow², n. > Sl

From the best English dictionary IMHO: https://www.ahdictionary.com/word/search.html?q=wow https://www.ahdictionary.com/word/search.html?q=wow > wow², n. > Slow variation in the pitch of a sound reproduction resulting from variations in the speed of the recording or reproducing equipment.