Call up Definition 1 of 5Pro Tip 1/3Informal Chat Used when suggesting a friendly, informal conversation over the phone. Hey, let's call up John and chat about the weekend plans. Pro Tip 2/3Casual Follow-Up Suitable for casual follow-up or check-ins with someone you already know. I'll call you up next week to see how you're doing. Pro Tip 3/3No Agenda Implied Does not imply any formal agenda or serious subject unless specified. I might call you up sometime just to catch up.