unclean

What it means

1. Dirty, soiled or foul.

   They were gnawing, like beasts, upon unclean food. A pot boiled upon the edge of the fire, and out of it one of the creatures would occasionally drag a hunk of meat with a sharpened stick.

   1913, Edgar Rice Burroughs, The Return of Tarzan, New York: Ballantine Books, published 1963, page 194

2. Not moral or chaste.

   I stand amazed in the presence / Of Jesus, the Nazarene, / And wonder how He could love me, / A sinner, condemend, unclean.

   1905, Charles H. Gabriel, “My Savior's Love”, in E.O. Excell, editor, Praises, Chicago: E.O. Excell

3. Ritually or ceremonially impure or unfit.

In a sentence

They were gnawing, like beasts, upon unclean food. A pot boiled upon the edge of the fire, and out of it one of the creatures would occasionally drag a hunk of meat with a sharpened stick.

1913, Edgar Rice Burroughs, The Return of Tarzan, New York: Ballantine Books, published 1963, page 194

Where it comes from

1. Old Englishunclǣne
2. Middle Englishunclene
3. Englishunclean

From Middle English unclene, from Old English unclǣne, equivalent to un- + clean.