This is the 8518th most frequent French word.
allongés
Stretched out; elongated; lying down.
Here, 'allongées' is describing the shape of the leaves as elongated, functioning as an adjective modifying 'les feuilles'.
Les feuilles sont allongées et fines.
The leaves are elongated and thin.
In this sentence, 'allongés' is describing the action of 'nous,' indicating that we were in a reclining position, used as a past participle.
Nous étions allongés sous les étoiles.
We were lying down under the stars.
Here, 'allongé' is used as a verb (past participle) referring to the action of diluting or extending the coffee by adding water.