Simultaneous multithreading (SMT)

Wiki
Paper: Converting thread-level parallelism to instruction-level parallelism via simultaneous multithreading

SMT permits multiple independent threads of execution to better use the resources provided by modern CPU core.

Issue multiple instructions from multiple threads in one cycle. The processor must be superscalar to do so.

Hyper-threading Technology is intel’s implementation of SMT.
From Intel’s SDM Vol 1 section 2.2.8:

Each logical processor executes instructions from an application thread using the resources in the processor core. The core executes these threads concurrently, using out-of-order instruction scheduling to maximize the use of execution units during each clock cycle.

AMD Zen architecture processors also support SMT.