mare

1. the female of a horse or other equine animal.
2. a woman.

   that crazy mare put three bullets in him

Old English mearh ‘horse’, mere ‘mare’, from a Germanic base with cognates in Celtic languages meaning ‘stallion’.

1. a very unpleasant or frustrating experience.

   this week is going to be a bit of a mare but at least the end is in sight

1990s: abbreviation of nightmare.

1. a large, level basalt plain on the surface of the moon, appearing dark by contrast with highland areas.

   the maria are largely confined to the near side of the moon

   Mare Imbrium

mid 19th century: special use of Latin mare ‘sea’; these areas were once thought to be seas.