Nonaromatic Definition:

A compound that lacks a ring with a continuous system of overlapping
p orbitals.

Nonaromatic Explained:

A cyclic compound which doesn’t necessitate a continuous form of overlapping ring of p orbitals need not be considered as aromatic or even anti aromatic and hence these are termed as nonaromatic or aliphatic. Its electronic energy is similar to that of its open chain counterpart.