"Synoptic" is simply the adjectival form of "synopsis": Matthew, Mark, and Luke all strive to give a synopsis of Jesus' life, organized primarily around a chronological retelling of his approximately three-year ministry. Matthew and Luke include details of his birth and genealogy.
John, on the other hand, is organized around theological and moral themes, rather than the totality of Jesus' ministry and teachings. That's why it's not considered a synoptic gospel.
John, on the other hand, is organized around theological and moral themes, rather than the totality of Jesus' ministry and teachings. That's why it's not considered a synoptic gospel.