expression, i-adjective
loose; slack; not tight; relaxed; calm
Describes a lack of tension, tightness, or discipline. Often used for a relaxed atmosphere, a loose grip, or a person who is not on edge. The expression is synonymous with 締まりのない and だらしがない.
彼はいつもしまりがない顔をしている。
He always has a relaxed, easygoing expression.
このネジはしまりがないから
This screw is loose, so it comes off right away.
会議の雰囲気がしまりがなくて、なかなか話が進まなかった。
The meeting had a slack atmosphere, and we couldn't make much progress.
Synonymous expression; 締まりのない is the attributive form (modifying a noun), while しまりがない is a full predicate phrase.
Similar meaning of 'slovenly' or 'undisciplined', but だらしがない focuses more on personal untidiness or lack of self-control, whereas しまりがない can also refer to physical looseness or a relaxed atmosphere.
From 締まり (tightness, discipline) + がない (there is no). The word 締まり is the noun form of 締まる (to become tight).