plain

Dictionary definition · plain

extensive tract of level open land"they emerged from the woods onto a vast open plain"
a basic knitting stitch made by putting the needle through the front of the stitch from the lefthand side

express complaints, discontent, displeasure, or unhappiness"My mother complains all day"

clearly revealed to the mind or the senses or judgment"the effects of the drought are apparent to anyone who sees the parched fields"
not elaborate or elaborated; simple"plain food"
lacking patterns especially in color
not mixed with extraneous elements"plain water"
free from any effort to soften to disguise"the plain and unvarnished truth"
lacking embellishment or ornamentation"a plain hair style"
lacking in physical beauty or proportion"a homely child"

unmistakably (‘plain’ is often used informally for ‘plainly’)"the answer is obviously wrong"

Source: Open English WordNet (CC BY 4.0).