Medical Definition of mm Hg
: a unit of pressure equal to the pressure exerted by a column of mercury 1 millimeter high at 0°C and under the acceleration of gravity and nearly equivalent to 1 torr (about 133.3 pascals) The pulse was 110 beats per minute and the blood pressure was 105/60 millimeter Hg …—Michael Drancourt et al., The New England Journal of Medicine, 16 Feb. 1995 34% of treated eyes had only a transient rise in intraocular pressure of 5 millimeter Hg or more …—David Frankel, The Lancet, 27 Dec. 1995
Seen and Heard
What made you want to look up mm Hg? Please tell us where you read or heard it (including the quote, if possible).