The term "three-line head" is typically used to describe a certain format or structure of writing. It refers to a style of writing that consists of three succinct lines that convey a message or idea. Some synonyms for this term may include "triptych," "tercet," "triplet," or "haiku." These words all refer to a format of poetry or writing that consists of three lines, each with a specific syllable count or rhyme scheme. While "three-line head" may be a more general term, these synonyms can help to convey a more specific meaning or style of writing to the reader.