Antonyms of adj infirm

2 senses of infirm

Sense 1
decrepit, debile, feeble, infirm, rickety, sapless, weak, weakly -- (lacking bodily or muscular strength or vitality; "a feeble old woman"; "her body looked sapless")

INDIRECT (VIA frail) -> robust -- (sturdy and strong in form, constitution, or construction; "a robust body"; "a robust perennial")

Sense 2
infirm -- (lacking firmness of will or character or purpose; "infirm of purpose; give me the daggers" - Shakespeare)

INDIRECT (VIA irresolute) -> resolute -- (firm in purpose or belief; characterized by firmness and determination; "stood resolute against the enemy"; "faced with a resolute opposition"; "a resolute and unshakeable faith")

Similarity of adj infirm

2 senses of infirm

Sense 1
decrepit, debile, feeble, infirm, rickety, sapless, weak, weakly -- (lacking bodily or muscular strength or vitality; "a feeble old woman"; "her body looked sapless")
       => frail (vs. robust) -- (physically weak; "an invalid's frail body")

Sense 2
infirm -- (lacking firmness of will or character or purpose; "infirm of purpose; give me the daggers" - Shakespeare)
       => irresolute (vs. resolute) -- (uncertain how to act or proceed; "the committee was timid and mediocre and irresolute")