IPA: //ʌnˈsɜːrˌpæsəbl//
KK: /ʌnˈsɜrˌpæsəbl/
Something that cannot be exceeded or improved upon; it is the best or highest quality possible.
Her performance in the competition was unsurpassable, earning her the top prize.
Unsurpassable → It is formed from "un-" (meaning not), "surpass" (from Old French *surpasser*, meaning to go beyond), and "-able" (meaning capable of). The word means not capable of being surpassed or exceeded.
Think of something that cannot be 'gone beyond' ('surpass') — the 'un-' means not, and '-able' means capable. This helps you remember that 'unsurpassable' refers to something that cannot be exceeded.