A more thorough explanation:

Definition: Unexpected is an adjective used to describe something that happens suddenly and without warning, something that was not anticipated or predicted. Example 1: The sudden rainstorm was unexpected, and we had to run for cover. Example 2: The surprise party was unexpected, and it was a great way to celebrate her birthday. Explanation: The first example shows how unexpected can be used to describe a sudden event that was not predicted, in this case, a rainstorm. The second example shows how unexpected can be used to describe a surprise event that was not anticipated, in this case, a surprise party. Both examples illustrate the definition of unexpected as something that happens without warning and is not expected.