a multipurpose greeting, taken from instant messenger transcript between former senator Mark Foley and his former congressional page. it was a typo for "boo dude", but is now used as a substitute for "hello" or any other salutation. there isn't necessarily any lewd connotation, but there certainly can be if desired.
Maf54 (7:25:14 PM): hey
Auto response from Xxxxxxxxx (7:25:14 PM): scrounging for food…brb
Maf54 (7:25:25 PM): ok
Maf54 (7:25:35 PM): kep scrounging
Xxxxxxxxx (7:31:51 PM): boo
Maf54 (7:32:13 PM): bo dude
Xxxxxxxxx (7:32:17 PM): lol
Person 1: bo dude!
Person 2: hey man, how's it going!
Person 1: great
Person 2: that's swell