IPA: /ˌʌnɪmˈprɛsɪv/
KK: /ʌnɪmˈprɛsɪv/
Not able to make a strong or positive impact; not impressive or noteworthy.
The presentation was quite unimpressive, failing to capture the audience's attention.
Unimpressive → It is formed from "un-" (meaning not) and "impressive" (from Latin "imponere", meaning to place upon or impose). The word "unimpressive" means not having a strong impact or failing to impress.
Think of 'not' ('un-') being added to something that 'imposes' or makes a strong impression — that's why unimpressive means it doesn't make a strong impact.