belle-mère

/bɛl.mɛʁ/
1.
nounfeminineSing

mother-in-law (the mother of one's spouse or partner)

On va dîner chez ma belle-mère ce week-end.

We're having dinner at my mother-in-law's this weekend.

2.
nounfeminineSing

stepmother (a woman married to one's parent)

Depuis que mon père s'est remarié, ma belle-mère prépare le dîner tous les soirs.

Since my father remarried, my stepmother has been making dinner every night.