pĕr-infirmus, a, um, adj.,
very weak or feeble : si quis perinfirmus est, Cels. 2, 14: sunt enim levia et perinfirma, quae dicebantur a te, Cic. Fin. 2, 16, 53; Cels. 2, 14 fin.
per-īnfīrmus adj., very weak. ...
An Elementary Latin Dictionary