Minimal means the smallest possible, or the least — as in, "She passed the test with minimal studying." Minimal can also mean simple, as in "The apartment had a minimal decor scheme: white walls, no art, a simple black couch."
When there is "minimal supervision" at a slumber party, few grownups are present. When you spend the "minimal amount of money" on a trip, you won't be staying at the Ritz. If you grew up with minimal contact with one of your parents, you barely saw or spoke to them. If you like to keep things simple, you might call yourself a minimalist, or a believer in minimalism.
adj the least possible
of questionable or minimal quality
so small as to be meaningless; insignificant
nominal, token, tokenish
insignificantly small; a matter of form only (`tokenish' is informal)
having only essential or minimal features