Synonyms for Unusable:

adj.

all (adjective)
unserviceable, unuseable.
impracticable (adjective)
inoperable, useless, unnegotiable.
useless (adjective)
impracticable, ineffective, unworkable, inadequate, detrimental, ineffectual, useless, good-for-nothing, nonfunctional, unserviceable, futile, unsuitable, impractical, worthless, inutile, fruitless.

n.

unnegotiable, limited, inferior, suboptimal, undistinguished, unsatisfactory, poor, disappointing, used, substandard, impracticable, average. ineffectual, inutile, worthless. unusable (noun)
useless, unserviceable, inoperable, unuseable.

Other synonyms:

inutile, unnegotiable. impracticable, ineffectual. worthless. Other relevant words:
impracticable, worthless, unuseable, inoperable, inutile, unnegotiable, ineffectual.