What is Janus-faced?

Janus-faced definition and meaning on Dictionary terms:

having two faces, one looking forward, one looking backward, as the Roman deity Janus.
having two contrasting aspects, as the alternation of mood in a capricious person.
two-faced; deceitful.
aware of or concerned with polarities; seeing different and contrasting aspects: a Janus-faced view of history.
having or containing contrasting characteristics: a Janus-faced policy.