Senses
一面 one side
one side or aspect of an object or situation
一面 [classifier]
for flat objects such as mirrors, flags, or walls
一面 once
(literary) Used to indicate meeting someone one time, as seen in the phrase 一面之交
一面 at the same time
Used to describe two or more actions happening simultaneously, often appearing in the pattern yī miàn... yī miàn...
一面 one's whole face
(literary) the entire face
一面 unilateral
one-sided; from one party only