Cert/sɜːrt/ Definition 1 of 2Pro Tip 1/3Colloquial Usage Used informally, mostly in conversations or casual writing. Their wedding next year? It's a cert. Pro Tip 2/3High Probability Suggests a very high chance of something occurring, almost guaranteed. If he runs, he's a cert for class president. Pro Tip 3/3Often Sports-Related Frequently used in the context of sports betting or predictions. With her record, she's a cert for the gold medal.