droop, wither, weaken, flag, dry up, shrivel, fade, go limp, become flaccid, lose freshness, faint.
Antonyms grow*, stiffen, stand*.
"wilt." YourDictionary, n.d. Web. 17 August 2018. <http://thesaurus.yourdictionary.com/wilt>.
wilt. (n.d.). Retrieved August 17th, 2018, from http://thesaurus.yourdictionary.com/wilt
To become limp, as from loss of freshness:
To hang limply, loosely, and carelessly: