"a breaking or bursting out, a violent issue," 1650s, from the verbal phrase; see out (adv.) + burst (v.). Outbresten was a verb in Middle English (mid-12c.), from Old English utaberstan. Carlyle (1837) apparently coined inburst (n.) to be its opposite.
an outburst of heavy rain
outbid
outboard
outbound
outbreak
outbuilding
outburst
outcast
outclass
outcome
outcrop
outcry