estaban estallando
-they/you were exploding
Imperfecto progresivo para el sujetoellos/ellas/ustedesdel verboestallar.

estallar

Anoche, los vecinos estaban estallando petardos y no me dejaban dormir.
Last night, the neighbors were setting off firecrackers and wouldn't let me sleep.
Palabra del día
el batidor