decibarMeteorol.|ˈdɛsɪbɑː(r)| [f. deci- + bar n.6 2.] A unit of barometric pressure equal to one-tenth of a bar. 1910,1914[see bar n.6 2].1967Oceanogr. & Marine Biol. V. 90 The difference between the geostrophic circulation at 1750 decibars and that at 1000 decibars is negligible.