Anything that alludes or refers to something else is referential. Many hip-hop songs are referential, using samples of other songs, mentioning them, or quoting them.
Your experimental poetry is referential, if it points directly or more subtly to sources and influences like Shakespeare and Britney Spears and Dr. Seuss. An architect might describe her modern designs as referential too, if they allude to older building styles, using Gothic arches and flat, Art Deco roofs. In general, the adjective referential is a fancy way to talk about the references, mentions, and allusions someone (usually an artist) makes to other things.