IPA: /nɒnˈpræktɪkəl/
KK: /nɑnˈpræktɪkəl/
Not useful or effective in real situations; not suitable for practical use.
The plan was deemed nonpractical and was quickly rejected by the committee.
Nonpractical → It is formed from "non-" (meaning not) and "practical" (from Latin "practicus", meaning effective or practical). The word "nonpractical" means not effective or not suitable for practical use.
Think of 'not' ('non-') and something that is 'effective' or 'useful' ('practical') — that's why nonpractical means something that is not useful in real situations.