xeriscape

Landscaping that does not require a lot of water. (US Dept of the Interior- Bureau of Reclamation)

xerophyte

Any plant growing in a habitat in which an appreciable portion of the rooting medium dries to the wilting coefficient at frequent intervals. (Plants typically found in very dry habitats.) (US Fish & Wildlife Service)

x-mark signature

A signature made by a person unable to sign his or her name. To be legally valid, the signature must be witnessed by another person. (Federal Reserve Bank- SF)