occasional

equivalents

infrequent

irregular

sporadic

unpredictable

synonyms

accessory

accidental

accompanying

additional

ado

adventitious

afloat

afoot

aleatory

auxiliary

behind the scenes

by-the-way

casual

casual

causal

causative

ceremonial

circumstantial

conditional

constitutive

contingent

current

decisive

determinative

doing

effectual

etiological

eventuating

extra

few

formative

going on

happening

in hand

in the wind

incidental

incidental

inessential

infrequent

institutive

intermittent

irregular

nonessential

occurring

odd

off

on

on foot

ongoing

originative

same-contexts

frequent

mere

small

sudden