Antonyms of adj suitable

2 senses of suitable

Sense 1
suitable, suited -- (meant or adapted for an occasion or use; "a tractor suitable (or fit) for heavy duty"; "not an appropriate (or fit) time for flippancy")

INDIRECT (VIA fit) -> unfit -- (below the required standards for a purpose; "an unfit parent"; "unfit for human consumption")

Sense 2
desirable, suitable, worthy -- (worthy of being chosen especially as a spouse; "the parents found the girl suitable for their son")

INDIRECT (VIA eligible) -> ineligible -- (not eligible; "ineligible to vote"; "ineligible for retirement benefits")

Similarity of adj suitable

2 senses of suitable

Sense 1
suitable, suited -- (meant or adapted for an occasion or use; "a tractor suitable (or fit) for heavy duty"; "not an appropriate (or fit) time for flippancy")
       => fit (vs. unfit) -- (meeting adequate standards for a purpose; "a fit subject for discussion"; "it is fit and proper that you be there"; "water fit to drink"; "fit for duty"; "do as you see fit to")

Sense 2
desirable, suitable, worthy -- (worthy of being chosen especially as a spouse; "the parents found the girl suitable for their son")
       => eligible (vs. ineligible) -- (qualified for or allowed or worthy of being chosen; "eligible to run for office"; "eligible for retirement benefits"; "an eligible bachelor")