1. Something extremely funny, perhaps causing an unusual amount of laughter.
2. A sarcastic term used to make fun of something.
Can also be spelled 'laugh-and-a-half'.
"Dude, did you see that crippled guy roll off the handicap ramp and flip over when his wheelchair ran out of battery power? Oh man, was that a laugh and a half! I'm so glad no one heard me cracking up there."
"So I went to that new restaurant that's been on every other commercial lately. I paid 15 dollars for a shrimp platter that only had 8 shrimp on it, and the rest of the dish was just lettuce and garnishes. Yeah, that place is a fucking laugh-and-a-half."