pĕr-imbĕcillus — Lewis & Short
pĕr-imbĕcillus, a, um, adj.,
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.