Definition from Wiktionary, the free dictionary
From metathesis of older *astellar, from astilla.
- to explode, to burst, to pop
- to crack (a whip)
- to break out, erupt; said of a revolution, a fire, or similar
- to break loose
- to blow up, to blow one's top
Conjugation of estallar (See Appendix:Spanish verbs)
1 Argentine and Uruguayan voseo prefers the tú form for the present subjunctive.