If you describe a person or their attitude or behaviour as unconventional, you mean that they do not behave in the same way as most other people in their society. Linus Pauling is an unconventional genius He had rather unconventional work habits, preferring to work through the night. conventional
An unconventional way of doing something is not the usual way of doing it, and may be rather surprising. The vaccine had been produced by an unconventional technique Despite his unconventional methods, he has inspired pupils more than anyone else conventional. very different from the way people usually behave, think, dress etc
not conforming to legality, moral law, or social convention; "an unconventional marriage"; "improper banking practices"