IPA: //nɒnˈsɛnsɪkəl//
KK: /nɑnˈsɛnsɪkəl/
Something that is silly or absurd and does not make sense.
The story was so nonsensical that I couldn't follow it at all.
Nonsensical → It is formed from "non-" (meaning not) and "sensical" (from "sense" derived from Latin "sensus", meaning perception or meaning). The word "nonsensical" describes something that does not have sense or meaning.
Think of 'not' ('non-') having 'meaning' ('sensus') — that's why nonsensical refers to something that lacks sense.