Often used to descibe a multi-oscillator mono-synth which can be configured to allow the oscillators to be controlled independently from the keyboard, allowing two or more notes to be played simultaneously. Classic string synths are typically paraphonic, and several modern multi-oscillator mono-synths can also work this way.
However, while the oscillators are controlled independently in a paraphonic synth, their outputs are all routed through the same filter / amp signal path and share the same envelopes. In contrast, a polyphonic synth has a separate filter/amp/envelope for each oscillator, all working completely independently.