Gigi Hadid's 'Armpit Hair' Apparently Wasn't Hair At All

Gigi Hadid wasn't trying to show off her unshaven pits during her LOVE Magazine photo shoot -- 'cause the fuzz folks saw was nothin' but loose fibers ... TMZ has learned.

Sources close to Gigi tell us her "armpit hair" -- which was prominently featured in day 11 of LOVE Magazine's Advent calendar video series -- was, in fact, residue left behind from the jacket she was wearing on set.

We're told the culprit was simply that navy cropped coat Gigi is seen wearing in the vid -- ya know, the one in which she's striking poses and kinda working up a sweat. Makes sense some of that could've gotten stuck to her.

What doesn't make sense is that no one on set saw the hairy stuff during the shoot, or even while editing the video.