A general exclamation, can be used to convey surprise, delight, pain, or simply to cover up awkward silences in conversation. A socially acceptable version of exclamations such as shit, fuck, wow, crikey, pants. Demonstrates a level of coolness unknown to most mortals.
Person 1:(can't think of anything to say)...that was Pants?
Person 2:(thinks)What a loser.
Person A:(can't think of anything to say)... 'Yaising!'
Person 2:(thinks) Wow, he's cool.