MBO — Mandatory Battles Only. A term for a playthrough or runthrough of a game where only battles required to be fought (forced encounters, boss battles, storyline battles) can be played. Any "traps" must be avoided, no sidequests or bonus dungeons may be completed if they cause obligatory battles, and all random encounters must be escaped from. The player is however allowed to gain however many levels they would like, unless paired with other restriction challenges.
Substitute "battles" for "missions" or other close-enough terms for games where it applies instead of battles.