occasional

a.偶然的；特殊场合的

obstructive, obstructively, obtain, obtainable, obtrude, obtrusion, obtrusive, obtrusive-ness, obtrusively, obtuse, obtuse angle, obtusely, obtuseness, obverse, obviate, obvious, obviously, obviousness, ocarina, occasion, occasional table, occasionally, Occident, Occidental, occlude, occult, occultist, occupancy, occupant, occupation, occupational, occupied, occupier, occupy, occur, occur to, occurrence, ocean, ocean lane, ocean-going,