المعنى الاصطلاحي

Lengthening the garment and lowering it beyond its Shariah bound (to the point that its lower end reaches below the ankles).

الشرح المختصر

"Isbāl" (lengthening the garment) is that when the man lets his garment reach below his ankles, whether it is an "izār" (waist sheet), "ridā" (cloak), "qamees" (long shirt), or "sirwāl" (pants); or lets the ends of his turban or the like hang below his back. "Isbāl" is of two types: 1. Forbidden "isbāl": when a man lengthens his garment below the ankles, whether out of pride and haughtiness or not. This is meant by the word "isbāl" when generally used. 2. Required "isbāl": when a woman lengthens her garment an extra handspan or cubit as a precaution to cover her "‘awrah" well.

التعريف اللغوي المختصر

"Isbāl": letting down. Original meaning: to let something hang down from a high place to a lower one, or extending something.