This word is acceptable for play in the US & UK dictionaries that are being used in the following games:

• Lexulous
• Wordscraper
• Wordosaur

In entomology, flat; forming a plane; flattened.

adj. having been flattened

"No one knows exactly how life on Earth will end, But scientists claim that a collision with Mercury or Mars could destroy our planate long before the Sun bakes it to a crisp in five billion years times."

two-dimensional    planar