IPA: //ʌnˈmɛmərəbəl//
KK: /ʌnˈmɛmərəbəl/
Something that is not easy to remember or does not leave a strong impression.
The movie was so unmemorable that I forgot the plot the next day.
Comparative: more unmemorable
Superlative: most unmemorable
Unmemorable → It is formed from "un-" (meaning not) and "memorable" (from Latin "memorabilis", meaning worthy of being remembered). The word "unmemorable" means not worthy of being remembered or forgettable.
Think of 'not' ('un-') being added to something that is 'worthy of being remembered' ('memorabilis'). This helps you remember that 'unmemorable' describes something that is forgettable.