self-ˈacting, ppl. a.
[self- 3 b, 4.]
1. Acting independently, without external impulse or influence. Also applied to motion characterized by such action.
| 1740 Cheyne Regimen 2 A Self-moving, self-acting secondary Agent. 1856 Grote Greece ii. xcvii. XII. 612 Self-acting Hellas. 1890 A. R. Wallace Darwinism 12 This self-acting process which..brings about change in the organic world. |
2. Mech. Acting automatically without the manipulation (or mechanism) which would otherwise be required. Also said of the operation.
| 1824 R. Stuart Hist. Steam Engine 84 The..self-acting mechanism of the Atmospheric Engines. Ibid. 85 Their simultaneous (rather than self-acting) operation. 1834–6 Barlow in Encycl. Metrop. (1845) VIII. 175/1 For the prevention of this [the unnecessary destruction of fuel], the self-acting damper has been invented. Ibid. 700/2 The machinery in the self-acting mule. 1869 Rankine Cycl. Mach. & Hand-tools Pl. F 3 The self-acting motion is obtained from the lever. Ibid. L 2 Self-acting radial drilling machine. 1875 Knight Dict. Mech. s.v., Self-acting Valve, one moved by the fluid, in contradistinction to one moved by the application of mechanical devices. |