flehmen

Flehmen comes to English by way of German, in which language the word applies to animals and means "to curl the upper lip." The German source of the English word is a verb, and the English word is also used-albeit rarely-as a verb, as in "the horse flehmened." More often, though, the verbal form is actually a gerund: "the horse's flehmening." "Flehmen" is sometimes capitalized in English, as nouns are in German, but more often it is lowercase.