IPA: //ˌʌn.ɪnˈflɛk.tɪd//
KK: /ʌnɪnˈflɛktɪd/
Describing a word that does not change form to show tense, mood, number, or case.
In English, the word 'sheep' is uninflected because it remains the same in both singular and plural forms.
Uninflected → It is formed from "un-" (meaning not) and "inflect" (from Latin "inflectere", meaning to bend or change). The word describes a form of a word that does not change or bend in its grammatical form.
Think of 'not' ('un-') changing or 'bending' ('inflect') — that's why uninflected means a word that does not change its form.