mesu メス

In Japanese, mesu メス means "female" or "scalpel," "shiv." Not to be confused with masu ます, the polite suffix.

When mesu メス means "female," it's also spelled mesu 雌, mesu 牝, and it's only used toward animals. The "male" counterpart would be osu オス, osu 雄, osu 牡.

Calling a woman mesu is like calling her an animal, which is degrading, derogatory. Which is why it does in fact happen, specially in anime where a character is throwing slurs at a woman, like "slut," bitch ビッチ.

In manga with surgeries, mesu メス also means the "scalpel" a surgeon uses to operate a patient.

Because a scalpel is a blade that opens people up, in manga with gangs, a mesu メス also refers to a shiv brandished in a fight. You know when two guys are fighting and then one guy—the bad guy, we know it's the bad guy—pulls out a shiv out of his pocket and brings a knife to a fist fight like some prideless cheater with no dignity? That's a mesu メス.