millimetre of mercury

https://doi.org/10.1351/goldbook.M03927
Non-SI unit for pressure; \(\text{mmHg}\approx 133.322\ \text{Pa}\). This old unit is not recognized by CIPM or ISO, but it is used for blood pressure.
Source:
PAC, 1996, 68, 957. (Glossary of terms in quantities and units in Clinical Chemistry (IUPAC-IFCC Recommendations 1996)) on page 981 [Terms] [Paper]