KEKWait is a variation of the popular KEKW emote, which is generally used when a KEKW moment "goes wrong" in some way. The image is a modified version of the KEKW emote and the meaning of KEKWait is something along the lines of "oh I didn't expect this to happen".
The KEKWait emote is a FrankerFaceZ extension Twitch emote which is a modified version of a popular cut-out of the face of Juan Joya Borja, a Spanish comedian and actor who’s also known as the Spanish Laughing Guy in internet circles. A popular YouTube video from a 2007 interview where Borja bursts into laughter while trying to tell an anecdote, revealing his almost toothless mouth and focusing on his exquisite moustache was turned into multiple memes by the Twitch community. KEKW, the original version, signifies hysterical laughter. KEKWait, in contrast, turns his smile upside down in this edit to indicate that a KEKW moment hasn't exactly worked out as planned. It was uploaded by foxboxx to FrankerFaceZ in November 2019.
In general, KEKWait is used as a counterpart to KEKW when an expected (funny) KEKW moment doesn't pan out as expected. Though Twitch chat users will usually just spam KEKWait without any text alongside it, it should work something like this in context:
Now that you know the meaning KEKWait has, how about further expanding your meme vocabulary? KEKW, its close counterpart, has an interesting story of its own, which you can check out here. What does monkaS mean? If you don't know, you might want to check out our article! There's also Pogchamp, the all-time great Kappa and many more Twitch emotes which are worth knowing about if you want to understand the brilliantly random content of Internet memes.