1 PHRASAL VERB 参军；入伍 If someone joins up, they become a member of the army, the navy, or the air force. 参军；入伍
2 PHR-V-RECIP （与…）联合；（与…）会合；（与…）组成联盟 If one person or organization joins up with another, they start doing something together. （与…）联合；（与…）会合；（与…）组成联盟
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Hawkins joined up with Mick in Malaga, and the two went touring around the countryside. [VERB PREP. with noun]
霍金斯在马拉加和米克会合，然后两个人到乡间游玩去了。
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Councils are joining up with their European counterparts. [VERB PREP. + with]
这些委员会将与欧洲的委员会结成联盟。
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They began to join up in communities. [V P + in]
他们开始结成团体。