(adj): vs. unipolar) -- (having two poles
(adj): marked by deliberate deceptiveness especially by pretending one set of feelings and acting under the influence of another
(adj): vs. honest), dishonorable -- (deceptive or fraudulent; disposed to cheat or defraud or deceive
(adj): having two faces--one looking to the future and one to the past
(adj): vs. faceless) -- (having a face or facing especially of a specified kind or number; often used in combination
Having two contrasting aspects. The name of the Roman god Janus comes from Latin ianua, an entrance gate. He was the god of doorways and gateways; as doors can be passed in either direction, he came to represent both the past and the future. Because of that, his image was of a man with two faces, looking both forwards and backwards. The Romans always put Janus first in prayers, because in particular he symbolised beginnings. But he could also represent success or failure, especially in war. He was the god of January, whose name comes from him (in Latin Januarius (mensis), the month of Janus), which had become the first month of the Roman calendar probably some time in the second century BCE. A person who is Janus-faced has two contrasting aspects and in particular is two-faced or deceitful. Israel Zangwill wrote a century ago that "Life is Janus-faced, and the humourist invests his characters with a double mask; they stand for comedy as well as for tragedy." A Janus-faced word is a contronym, a word like cleave that has two opposing meanings.
(from World Wide Words)