IPA: /ɪnˈvɛtərətli/
KK: /ɪnˈvɛtərɪtli/
In a way that is long-established and unlikely to change, often referring to habits or practices that are deeply ingrained.
He is inveterately late to every meeting, no matter how important it is.
Inveterately → It is formed from "in-" (meaning not) and "veterare" (from Latin, meaning to make old or to age) and the suffix "-ly" (meaning in a manner). The word describes a manner of being not just old but deeply established or habitual.
Think of something that is 'not' ('in-') just old but has become a deeply established habit over time — that's what inveterately means.