Godan verb with 'ru' ending
to be awash with; to teem with; to be full of
コンビニが女子であふれかえってて、押し分けて中にはいる気もせず、そのまま帰った。The convenience store was overflowing with girls, I didn't have the urge to push my way through them and went home as I was.
Also written 溢れ返る【あふれかえる】