IPA: /ˌʌn.rɪˈmɑːr.kə.bli/
KK: /ʌnˈrɛmɑrkəbli/
In a manner that is not interesting or noteworthy; without any special features or qualities.
The movie was unremarkably average, failing to impress the audience.
Unremarkably → It is formed from "un-" (meaning not) and "remarkable" (from Latin "remarcabilis", meaning worthy of notice). The word "unremarkably" means not worthy of notice or ordinary.
Think of 'not' ('un-') being added to 'worthy of notice' ('remarkable') — that's why unremarkably means something that is ordinary or not special.