Antonyms of adj usable

3 senses of usable

Sense 1
useable, usable -- (capable of being put to use; "usable byproducts")

INDIRECT (VIA useful) -> useless -- (having no beneficial use or incapable of functioning usefully; "a kitchen full of useless gadgets"; "she is useless in an emergency")

Sense 2
functional, usable, useable, operable, operational -- (fit or ready for use or service; "the toaster was still functional even after being dropped"; "the lawnmower is a bit rusty but still usable"; "an operational aircraft"; "the dishwasher is now in working order")

INDIRECT (VIA serviceable) -> unserviceable -- (not ready for service; "unserviceable equipment may be replaced")

Sense 3
available, usable, useable -- (convenient for use or disposal; "the house is available after July 1"; "2000 square feet of usable office space")

INDIRECT (VIA disposable) -> nondisposable -- ((of assets) unavailable for use)

Similarity of adj usable

3 senses of usable

Sense 1
useable, usable -- (capable of being put to use; "usable byproducts")
       => useful (vs. useless), utile -- (being of use or service; "the girl felt motherly and useful"; "a useful job"; "a useful member of society")

Sense 2
functional, usable, useable, operable, operational -- (fit or ready for use or service; "the toaster was still functional even after being dropped"; "the lawnmower is a bit rusty but still usable"; "an operational aircraft"; "the dishwasher is now in working order")
       => serviceable (vs. unserviceable) -- (ready for service or able to give long service; "serviceable equipment"; "heavy serviceable fabrics")

Sense 3
available, usable, useable -- (convenient for use or disposal; "the house is available after July 1"; "2000 square feet of usable office space")
       => disposable (vs. nondisposable) -- (free or available for use or disposition; "every disposable piece of equipment was sent to the fire"; "disposable assets")