IPA: /ɪmˈprɒbəbli/
KK: /ɪmˈprɑːbəbli/
In a way that is unlikely to happen or be true.
She improbably won the lottery twice in a row.
Improbably is formed from "im-" (meaning not) and "probabilis" (from Latin, meaning provable or likely) and the suffix "-ly" (meaning in a manner). The word describes something that is not likely to happen or is unlikely.
Think of 'not' ('im-') making something 'likely' ('probabilis') — that's why improbably means something that is not likely to occur.