pĕr-imbĕcillus

I. 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.