IPA: /ˌʌn.rɪˈmɑːr.kə.bəl/
KK: /ʌnˈrɛːmɑːrkəbl/
Something that is not special or different; it is ordinary and does not stand out.
The movie was unremarkable and didn't leave a lasting impression on the audience.
Unremarkable → It is formed from "un-" (meaning not) and "remarkable" (from Latin "remarcabilis", meaning worthy of notice). The word "unremarkable" means not worthy of notice or ordinary.
Think of 'not' ('un-') being added to 'worthy of notice' ('remarkable') — that’s why unremarkable means something that is ordinary and not special.