<interjection> Chiefly Anglo-Scottish Slang;
Used to express a sexual attraction to another person.
--> The term is abnormal; There is no definite rule to using the word. Although, being an interjection, a rule of thumb would be to use it in the same way as "Wow." It is kind of the same as saying, "Hey, I want to shag you!" only in a single word.
As with most slang, the only way you can use it is how you feel it should be used...
Nickname given to bales of marijuana thrown overboard or out of airplanes. Origin is reportedly from members of the US Coast Guard in the area of Southern Florida.
"Base we've got some square groupers floating outside of Miami harbor."