adventitious
adjective
[ ˌadv(ə)nˈtɪʃəs ]
• happening as a result of an external factor or chance rather than design or inherent nature.
• "adventitious similarities"
Similar:
unplanned,
unpremeditated,
accidental,
unintentional,
unintended,
unexpected,
unforeseen,
involuntary,
chance,
fortuitous,
serendipitous,
coincidental,
casual,
random,
fluky,
unlooked-for,
unhoped-for,
not bargained for,
out of the blue,
without warning,
aleatory,
Opposite:
planned,
Origin:
early 17th century: from Latin adventicius ‘coming to us from abroad’ (from advenire ‘arrive’) + -ous (see also -itious2).
