This is the 5782nd most frequent Russian word.
профсоюзов
"Профсоюзов" means "trade unions."
In this sentence, 'профсоюзов' specifies the collective group of trade unions organizing a meeting.
Собрание всех профсоюзов состоится в пятницу.
The meeting of all trade unions will take place on Friday.
The word 'профсоюзов' here emphasizes the functioning and activism of trade unions.
Интересы рабочих часто защищаются через деятельность профсоюзов.
The interests of workers are often protected through the activities of trade unions.
Here, 'профсоюзов' refers to trade unions in general as the subject of the sentence.