Antemeridian is a term used to describe something that occurs before noon or in the morning. Other synonyms for antemeridian include the words "AM," "forenoon," "morning," and "A.M. hours." Each of these words can be used interchangeably with antemeridian depending on the context of the sentence. For example, if you were to say "I am only available in the AM hours," that would be the same as saying "I am only available antemeridian." Similarly, if you were to say "I have a meeting in the forenoon," that would be another way to say "I have a meeting before noon" or "I have a meeting antemeridian".