weakly /ˈwiːkli/adjective 1adverb 1forms 4 adjective1 •Frail, sickly or of a delicate constitution; weak.I lay in weakly case and confined to my bed for four months before I was able to rise and health returned to me. — 1885 adverb1 •With little strength or force.The basitemporal platform is flat in posterior view because the mamillar tuberosities are very weakly developed. — 2002 formsmore weakly · weaklier · most weakly · weakliest