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In the context of switch performance, generally a non-blocking switch's interior bus/fabric offers enough bandwidth that meets, or exceeds, the aggregate bandwidth of all its ports. However, even if that's true, some switch architectures can block traffic due to head-of-line blocking, i.e. congestion on one port blocks another uncongested port or ports. (NB: "modern" switch architectures usually don't have HoL blocking as a possible issue.)
Also even if a switch is non-blocking, regarding its interior bandwidth, wire-speed/line-rate requires the switch's frame/forwarding support full bandwidth with minium size frame/packets.
So to recap, non-blocking really means there's sufficient bandwidth, wire-speed/line-rate really means frame/packet forwarding supports full bandwidth regardless of frame/packet sizes.
