unsatisfactory; not acceptable / (linguistics) not conforming to accepted usage

Something that is not acceptable.

not having any authority / without official authorization

Not handsome or beautiful or appealing. / Lacking the power to attract interest.

An aesthetically unattractive person

so unpleasant or painful as to be unendurable

modest and having no pretensions or ostentation

Impossible to avoid; bound to happen. / (law) Not voidable; incapable of being made null or void.

Something that cannot be avoided.

Defenceless and lacking weapons or armour. / Not carrying arms. / (biology) Not having thorns or claws etc. / (obsolete) Unaided, as of the vision without a glass.