| Hydropneumatic | a. [ Hydro-, 1 + pneumatic: cf. F. hydropneumatique. ] Pertaining to, or depending upon, both liquid and gaseous substances; |
| Hydropneumatic gun carriage | . (Ordnance) A disappearing gun carriage in which the recoil is checked by cylinders containing liquid and air, the air when compressed furnishing the power for restoring the gun to the firing position. It is used with some English and European heavy guns. [ Webster 1913 Suppl. ] |