This is a regular verb with a spelling change. It follows the conjugation pattern of the verb abrazar.
Spelling Change: ze ce - zé cé
PresentPresente
El niño bosteza porque tiene sueño.
The boy yawns because he is sleepy.
ImperfectPretérito imperfecto
Los estudiantes bostezaban durante la clase aburrida.
The students were yawning during the boring class.
PreteritePretérito indefinido
Ayer bostecé tres veces en la reunión.
Yesterday I yawned three times in the meeting.