[duhb-uh
l-ak-ting] 
| 1. | (of a reciprocating engine, pump, etc.) having pistons accomplishing work in both directions, fluid being admitted alternately to opposite ends of the cylinders. Compare single-acting. |
| 2. | (of a hinge of a door or the like) permitting movement in either direction from the normal, or closed, position. |
| 3. | having twice the usual effectiveness, strength, use, etc. |