Meaning of cho(ちょ)

It means “just a minute” or “wait a minute”, it’s an abbreviation for “chotto matte(ちょっと 待って)”.
“chotto(ちょっと)” means a little. “matte(待って)” means a wait.
Cho is a slang.
Choma(ちょま)” is also same meaning and an abbreviation for “ちょっと 待って”.

Example Conversation

A: Oh, do you like Kayo?
B: yeah…kind of… but I’ve never talked with her…
A: Then let’s ask her to hang out! I know her LINE, so I do it right now!
B: Oh, cho, it’s too fast isn’t it? Wait! Wait!

A: え、おまえ佳代のこと好きなの？
B: いやー、まぁ。でも喋ったことないんだよね…。
A: じゃあ今度の飲み会誘おうぜ！あ、俺ライン知ってるから誘っちゃうね！
B: え、ちょ、展開早くない？待って！待って！