A mindscape is the mental landscape of a sentient being.

Perception of time became malleable inside the mindscape of a Vulcan mind meld. (ST - Mirror Universe novel: Rise Like Lions)

T'Pol had encounters with Trip Tucker in her mindscape. (ENT novel: Kobayashi Maru)

A Klingon machine merged the minds of James T. Kirk, Spock and Leonard McCoy, but Spock was able to pull them all out of his mindscape. (TOS - Constellations short story: "Chaotic Response")

When T'Prynn mind melded with Cervantes Quinn, she interpreted their shared mindscape as a virtual world. (VAN novel: Storming Heaven)

When Soleta mind melded with Sela, she saw a gigantic image of Sela in her mindscape. (TNG - Double Helix novel: Double or Nothing)

When Ezri Dax made mental contact with the Annuated, she initially experienced the mindscape as falling through an ocean of experience, but quickly converted it into a white backdrop filled with spheres representing memories, the oldest of which lay closest to the center. (DS9 - Worlds of Star Trek: Deep Space Nine novel: Trill: Unjoined)