Definition of "Plain" :

noun: a basic knitting stitch made by putting the needle through the front of the stitch from the lefthand side

noun: extensive tract of level open land

"They emerged from the woods onto a vast open plain."

verb: express complaints, discontent, displeasure, or unhappiness

"My mother complains all day."

adjective: lacking embellishment or ornamentation

"A plain hair style."

adjective: lacking in physical beauty or proportion

"A plain girl with a freckled face."

adjective: free from any effort to soften to disguise

"The plain and unvarnished truth."

adjective: clearly revealed to the mind or the senses or judgment

"Made his meaning plain."

adjective: lacking patterns especially in color

adjective: not elaborate or elaborated; simple

"Plain food."

adjective: not mixed with extraneous elements

"Plain water."

adverb: unmistakably (plain' is often used informally for plainly')

"You are plainly wrong."