look up any word, like the eiffel tower:
 
1.
a term definitive to someone who repeatedly has sexual intercourse with less than desirable women. The unattractive women are the flags, and stacker means he's stacking them up.
"That nigga Jim a flagstacker fo' real"
"Man, did you see Jonny last night? He stacked 6 flags dawg"
"Flagstacking ass niggas up in this bitch tonight"
by BigJimandShady July 29, 2012