1 [only before noun]
a conventional method, product, practice etc has been used for a long time and is considered the usual type:
Internet connections through conventional phone lines are fairly slow.
Bake for 20 minutes in a conventional oven; 8 in a microwave.
always following the behaviour and attitudes that most people in a society consider to be normal, right, and socially acceptable, so that you seem slightly boring:
a strong believer in conventional morals
He is conventional in his approach to life.
the opinion that most people consider to be normal and right, but that is sometimes shown to be wrong:
As traffic grew, the conventional wisdom was to widen the roads.
4 [only before noun]PMW
conventional weapons and wars do not use nuclear explosives or weapons:
the usual form of medicine practised in most European and North American countries [= western medicine]
—conventionality noun [uncountable]