unsuccessful, a. [unfortunate], [unlucky], unprosperous; [abortive], [fruitless], [unavailing], [bootless], ineffectual, [futile].
unsuitable, a. [inappropriate], incongruous, incompatible.
unsupplied, a. [destitute].
unsurmountable, a. insuperable.
unsurpassed, a. [peerless], transcendent, [superior], [unrivaled], [matchless].
unsusceptible, a. unimpressionable, [unfeeling].
unsuspecting, a. unsuspicious, [gullible], [credulous], indubious, [unsophisticated].
unsustainable, a. untenable, controvertible.
untangle, v. [unravel], disentangle.
untaxed, a. scot-free, exempt.