IPA: /ʌnˈtʃɛkt/
KK: /ʌnˈtʃɛkt/
Not controlled or limited; allowed to happen without any restrictions or checks.
The unchecked growth of the weeds took over the entire garden.
Unchecked → It is formed from "un-" (meaning not) and "checked" (from Old English "cecan", meaning to examine or verify). The word "unchecked" means not examined or verified, implying a lack of control or restraint.
Think of something that is 'not' ('un-') 'examined' ('checked') — that's why unchecked means it hasn't been verified or controlled.