1. visit someone/somewhere briefly
call in to see someone
As a phrasal verb 'call in' means 'to visit' someone or somewhere. "I need to call in to my grandmother's to see if she needs anything." You could call into someone's home or call into a shop for example. In this usage, similar meaning phrases are 'pop in' and 'drop in on'. This is a commonly used phrasal verb in social and professional situations. Note: 'call-in' and 'call-in' can also be used as a verb or a noun and can mean 'to phone in' to a radio station or TV programme. It can also be used to refer to the kind of TV or radio show were the public can use their phone to talk to the hosts: 'a call-in show' or it can mean to invite someone to ask them to help you in some way "We should call in the help of a solicitor for this.".