Meaning of “riatai”(リアタイ)
It means “in real time” or “live”.
“riatai” is an abbreviation of “realtime”(リアルタイム).
Yes, Japanese always want to make words 4 characters.
Example Conversation
A: You can watch the game on NHK tonight.
B: Really? Oh, I’ll watch it and do riatai tweet.
A: その試合は今晩NHKでやるよ
B: まじで? あー、見ながらリアタイツイートしようっと。