mare'sˈ-tail noun

1. A tall marsh plant of the genus Hippuris
2. Also applied to the horsetail
3. (in pl) long straight strands of grey cirrus cloud

the grey mare is the better horse

The wife rules her husband, or is the more able partner

mare² /māˈrē or -ri, marˈe or -i/

Any of various darkish level areas on either the Moon or Mars

mare clausum /klöˈsəm, klowˈsŭm/ noun (Latin)

1. A closed sea
2. A sea within the jurisdiction of one state

mare liberum /libˈə-rəm, lēˈbe-rŭm/ noun (Latin)

A sea open to free navigation by ships of any nation

mare³ /mār/

1. A folkloric evil spirit that terrifies or suffocates the sleeping person (Shakespeare)
2. A calamitous experience (slang)