Heptastich refers to a poem or verse that consists of seven lines. There are several synonyms for heptastich, including septet, seven-line poem, seven-liner, and seven-line verse. While all of these terms refer to the same type of poem, some may be more commonly used than others. Other possible synonyms include seven-line strophe and heptameter. It is important to note that while these terms may be used interchangeably, they do not necessarily apply to all types or styles of poetry, as different forms of poetry may have their own unique structures and requirements.