1. a mistake or a fumble
Professional
Social
a slip-up at work, always slipping up
This can be used to mean a mistake or to imply clumsiness in one's work or dealings with others. It is a popular way of talking about errors: "I may have slipped up with the figures there. Let me re-check them for you." "Please don't slip up in this meeting. This contract is vital to our company." This is an expression you will hear in social and professional contexts. Similar meaning expressions include 'make a blunder' and 'get it wrong'.