This is the 6149th most frequent Russian word.
супругом
"Супругом" means "spouse" (male) in English.
In this sentence, "супругом" means "husband," referring to the spouse of the sister.
Я увидел, как моя сестра разговаривает с супругом.
I saw my sister talking with her husband.
Here, "супругом" indicates "husband" as the person accompanying the speaker.
Мы пришли на конференцию с супругом.
We came to the conference with my husband.
In this case, "супругом" denotes "husband" showing the relationship between the individual mentioned and their spouse.