A dim-witted, oblivious and/or inattentive woman.
"dinghy" in this phrase is a shortened variation of dingbat and should not be confused with dingy (pronounced "din-jee") meaning dirty or soot-covered.
I'm not repeating myself a third time, ya dinghy broad!
a dirty slutbag who deserves no respect
"Greer you're such a fuckin dinghy broad!"