The name means, literally, "joy".
Also, Bucur is a Romanian legendary figure, similar to the Greek Satyrs and Centaurs. Depictions show him as a half-human, half-horse figure, usually in a warrior pose. The name is derived from the said founder of the country's capital city - Bucuresti [Bucharest].
He is believed to be a very smart, witty and charming entity, sexually potent and desirable - unlike the Southern relatives, who were synonims to depravation, immorality and brutality. Modern urban myths seem to emerge, slowly turning the word into a common adjective, attaching all the above mentioned qualities.
Examples:
[upon someone achieving something] "...esti Bucur, ce mai..." - "...you're truly Bucur..."
[after a hot night] "...e Bucur in pat, n-as fi zis..." - "...he's a Bucur in bed, i wouldn't have tought..."