Definition of frails:
(adj) :
Easily broken physically; not firm or durable; liable to fail and perish.
(adj) :
Weak; infirm.
(adj) :
(medicine) In an infirm state leading one to be easily subject to disease or other health problems, especially regarding the elderly.
(adj) :
Liable to fall from virtue or be led into sin; not strong against temptation; weak in resolution; unchaste.
(adj) :
Mentally fragile.
(n) :
(dated, slang) A girl.