俯せる is the potential of 俯す

1. Godan verb with 'su' ending, Intransitive verb

   to lie face down (e.g. on the ground, napping on a desk); to lie prone

2. to lower (one's head, gaze, etc.)

   Archaic

Also written うつ伏す【うつぶす】utsubusu、俯伏す【うつぶす】utsubusu