8e948578_l_Verbs___Common_Phrasal_Verbs__Phrasal_Verb
[Meaning] To engage in, become a member of To meet and unite with [Example] There was a war on, so some kids were only sixteen when they joined up. Let’s separate now and join up later at the restaurant. [Phrasal Verb] 
join up
An Extensive List of Phrasal Verbs | Common Phrasal Verbs
Phrasal Verb