Synonyms in taxonomy are similar to normal synonyms, there are two (or more than two) names for the same thing in a scientific classification. For example, the cat has a few scientific names in: Felis silvestris catus, Felis catus, and Felis catus domestica.
In botany, the word "synonym" has a special meaning. There is one "correct name", and the other names are synonyms. For example, Daemonorops draco is the correct name of a species of palm trees, and Calamus draco is a synonym for the same species.
In zoology, there is one "valid name" and the others are "junior synonyms".
Synonym (taxonomy) Facts for Kids. Kiddle Encyclopedia.