In this context: an action oft-considered unusual, embarrassing, frowned upon, dangerous or difficult, performed with relative ease and more importantly with a relaxed, indifferent air.
Often misused for actions that are completely normal and of no interest to others e.g. "Casually watching a particular DVD".
Casually sharing my sandwich with a lion today.
Casually strolling through the street in my pyjamas carrying nothing but toilet roll this morning.
Dating with out the pressure of a serious relationship. Often times a vauge reference to a loose relationship, although it doesn't have to be a sexual relationship. Casual dating can be a confusing term.
The sexual orientation of one who is completely straight but it quite comfortable talking about another member of the same sex in a midly sexual manner.
"'yeah, he's certainly got a nice firm butt'"
is casually straight, however
"'i would like to rag him one up the jacksie'"
is generally not considered casually straight and more quite simply gay.
Pajama casual is a term used when working from home and preparing for a video conference. All business above the waist and your pajama pants down below.