IPA: /nɒnˈsɪmɪtrɪkəl/
KK: /nɑnˈsɪmɪtrɪkəl/
Not having the same shape or size on both sides; lacking symmetry.
The design of the building is nonsymmetrical, with one side being much larger than the other.
Nonsymmetrical → It is formed from "non-" (meaning not) and "symmetrical" (from Greek "symmetria", meaning proportion or measure together). The word "nonsymmetrical" means not having symmetry or not being proportionate in shape or arrangement.
Think of 'not' ('non-') having 'proportion' or 'measure together' ('symmetria') — that's why nonsymmetrical means lacking symmetry.