IPA: /ɪmˈpræktɪkəl/
KK: /ɪmˈpræktɪkəl/
Not suitable or effective for practical use; difficult to implement or carry out in real situations.
The plan to build a bridge made of candy was deemed impractical by the engineers.
Impractical is formed from "im-" (meaning not) and "practical" (from Latin "practicus", meaning able to act or do). The word describes something that is not suitable for practical use or application.
Think of 'not' ('im-') being combined with 'able to act' ('practicus') — that's why impractical means something that cannot be effectively used.