IPA: /ˌʌn.kəˈlɛk.tɪd/
KK: /ʌnˈkɒlɛktɪd/
Not gathered or picked up; refers to things that have not been collected or organized.
The uncollected trash began to attract pests in the neighborhood.
Uncollected → It is formed from "un-" (meaning not) and "collected" (from Latin "colligere", meaning to gather together). The word "uncollected" means not gathered together or not assembled.
Think of 'not' ('un-') gathering things together ('collected') — that's why uncollected means things that are not gathered.