Well, it's very CASUAL. No dress code or...
The Big Bang Theory Season 2, Episode 10
Is there some new kind of Casual Friday
I don't know about?
The Big Bang Theory Season 2, Episode 5
...and engage in CASUAL physical contact...
The Big Bang Theory Season 6, Episode 1
I've extended a friendly,
CASUAL greeting.
The Big Bang Theory Season 3, Episode 10
...to provide Amy with conversation
and CASUAL physical contact.
The Big Bang Theory Season 6, Episode 1