i-adjective
Colloquial, often derogatory or teasing way to describe someone or something as physically weak, frail, or lacking strength. Similar to 弱々しい but more casual and emotive.
See also: 弱々しい
あいつは見かけ倒しで、意外と弱っちいんだよ。
That guy is all show; he's surprisingly weak.
This desk is so flimsy it looks like it'll break any minute.
弱々しい is a standard, neutral adjective meaning 'weak-looking' or 'frail'. 弱っちい is a colloquial, often derogatory synonym with a stronger emotional tone.
弱い is the basic word for 'weak'. 弱っちい adds a colloquial, belittling nuance, similar to 'puny' or 'wimpy'.
Derived from the adjective stem 弱 (yowa-) with the colloquial suffix っちい (-tchii), which adds an emotive, often derogatory nuance. The exact origin of the suffix is uncertain, but it may be related to similar colloquial formations like ちっちゃい (small).