irresponsible; careless; perfunctory
Negative na-adjective for actions, work, attitudes, or people that are sloppy, unreliable, or done without proper care.
You can't entrust important work to an irresponsible person.
The customers got angry at the shop's careless service.
half-baked; halfhearted; vague
Used when information, plans, knowledge, explanations, or effort are not properly developed, precise, or committed.
Explaining with half-baked knowledge will only cause more confusion.
His explanation was vague, and the key points were not clear.
enough already; cut it out
Used to express irritation or a wish for something to stop, especially in fixed patterns such as いい加減にして and いい加減にしろ.
See also: いい加減にする
Enough with the jokes.
Cut it out with that story already.
Adverbial use meaning something has reached a considerable degree; often conversational and may carry a slight 'by now' or fed-up feeling.
These shoes have gotten pretty old.
After walking nonstop since morning, I'm quite tired.
He's a pretty irresponsible person, so it's better not to trust him too much.
The teacher confused the students by saying something vague and half-baked.
I'm pretty exhausted by now, so let's stop for today.
いい加減 stresses sloppiness and lack of thoroughness, whereas 不真面目 focuses on lacking seriousness or sincerity in attitude.
いい加減 emphasizes carelessness or irresponsibility in doing something, while 中途半端 focuses on the unfinished, half-done result of that attitude.
いい加減 covers being irresponsible or half-hearted in general conduct, while だらしない is more specifically about untidiness or lax self-control.
いい加減 describes a careless, halfhearted attitude, the opposite of the focused earnestness of 真剣.
いい加減 describes doing something carelessly or half-heartedly, the opposite of the meticulous care implied by 念入り.
いい加減 describes doing something halfheartedly or carelessly, the opposite of みっちり's thorough, rigorous effort.