millibarn.

1910 V. Bjerknes et al. Dynamic Meteorol. & Hydrogr. i. i. 7 It will be necessary for us to have names for the employed units of pressure..some name derived from the word ‘barometer’. We shall choose the name bar as being the shortest, and designate the decimal parts of it as the decibar, centibar, and millibar.

1914 Q. Jrnl. Royal Meteorol. Soc. 40 187 The megadyne per square centimetre has been adopted and called the ‘bar’... The bar is less convenient for printing and conversation than the millibar, its 1/1000th part, and the latter has therefore been generally adopted; it is equivalent to the pressure produced by about three-hundredths of an inch of mercury or by three-quarters of a millimetre.

1924 Glasgow Herald 23 Dec. 5 So far as I can judge from the synoptic chart for December 9, 7 a.m.,..the pressure at New Pitsligo at 7 a.m. seems to have been 1016 millibars, and by noon to have risen to about 1012 millibars, equivalent to 30·12 inches.

1942 V. C. Finch et al. Elem. Meteorol. v. 104 ¹/ ₁₀ inch on a barometer or barograph is equivalent to about 3 millibars. Either inches or millibars may be used in numbering the isobars on a weather map.

1984 A. C. Duxbury & A. Duxbury Introd. World's Oceans vii. 212 The average atmospheric pressure at sea level is 1013.25 millibars.

1993 K. S. Robinson Green Mars (new ed.) 200 If wielded on the surface to anywhere near its full capacity, it would volatise hundreds of millibars of gases into the atmosphere.