the definition of yada is basically randomness. some people will use so be like yada, yada, yada, blah, blah, blah but dont use it like that. when you just want to say something random, say yada.
person 1: what should we talk about
person 2: idk
both: (sigh)
person 2: yada!
Yada. Yada will be used while talking or in the place of boredom as a random word to fill up space
You are talking in a conversation and you stop talking then randomly want to say something. You would say yada