IPA: //ʌnˈspɛktəkjʊlər//
KK: /ʌnˈspɛktəˌkjʊlər/
Not impressive or exciting; ordinary or unremarkable.
The movie was quite unspectacular, lacking any thrilling moments.
Unspectacular → It is formed from "un-" (meaning not) and "spectacular" (from Latin "spectaculum", meaning a show or sight). The word "unspectacular" means not impressive or lacking in showiness.
Think of 'not' ('un-') being added to 'show' ('spectacular') to remember that 'unspectacular' means something that does not impress or stand out.