"to fall out, to fall (snow), to befall" is Выпасть in Russian.
Выпасть means "to fall out, to fall (snow), to befall" in English.
Listen to the pronunciationWord #3204 of 4,000 by frequency in Russian — level B2.
Ключи могли выпасть из кармана.
The keys could have fallen out of the pocket.