1. Having two faces--one looking to the future and one to the past
   - two-faced 
2. Marked by deliberate deceptiveness especially by pretending one set of feelings and acting under the influence of another
   - ambidextrous, deceitful, double-dealing, duplicitous, two-faced, double-faced, double-tongued 
3. Having or concerned with polarities or contrasts
   "a Janus-faced view of history"; "a Janus-faced policy"

See also: bipolar, dishonest, dishonorable [US], dishonourable [Brit, Cdn], faced

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