It's when you have an orgasm during yoga or a particular yoga position-which makes sense especially with certain yoga that can be extremely physical so it really gets the muscles going not to mention the blood flowing. For those who don't know much about yoga it is very spiritual and visceral all at once.
A: I had a major yogasm today after class...
B: Ha! Tell me about it...I know all too well.
When you have an enhanced orgasm by sleeping with someone from your yoga class, the climax of the tantric yoga experience. Made popular by the character Samantha on Sex in the City, who was so horny that she left yoga class with another student to go fuck.
That was an awesome yogasm! The side crow pose is really paying off!