pĕr-imbĕcillus, a, um, adj.,
very weak or feeble : collum anserum, Varr. R. R. 3, 10, 5: quod quidem est natum perimbecillum est, Cic. Att. 10, 18, 1: verbum, Sulp. Sev. Chron. 2, 17, 3.
per-imbēcillus adj., very weak, helpless. ...
An Elementary Latin Dictionary