Nickname for Marg Helgenberger of CSI. Given to her by Gary Dourdan at the time of Fergie's "Fergalicious" came out. Marg's fans have come to use the nickname to describe anything pertaining to Marg (or otherwise) as lovely, sexy, sweet, gorgeous, smart, funny, witty, sassy, adorable, eye candy, perfect, etc.
Did you see last night's CSI? It was so Margalicious!
Margalicious is when somebody is 'marga' (as in the Caribbean word for slim/skinny) yet 'delicious' at the same time, the amalgamation of words becoming 'MARGALICIOUS'.
That guy/girl is really skinny but margalicious all the same, mmmmmm.