The OG thick/thicc just meant pear shaped, likely muscular without being fat. But fats have polluted the term just as they do everything in their vicinity so now it means fat (usually not planet status though) but pear shaped. My sister is the classic thick, small waist & upper body but human sized and carries everything in the butt & thighs. But now she is what is referred to as slim-thicc, i.e. human sized with ass & thighs.