IPA: /ˌnɒn.sɪm.əlˈteɪ.ni.əs/
KK: /nɑnˈsɪməlˌteɪniəs/
Not happening at the same time; occurring at different times.
The two events were nonsimultaneous, with one taking place in the morning and the other in the evening.
Nonsimultaneous → It is formed from "non-" (meaning not) and "simultaneus" (from Latin "simul" meaning at the same time and "-aneus" meaning pertaining to). The word describes events that do not occur at the same time.
Think of 'not' ('non-') happening 'at the same time' ('simultaneus') — that's why nonsimultaneous means events that do not occur together.