self-ˈactorMech. [self- 4.] A self-acting mule in a spinning-machine. 1835Ure Philos.Manuf. 40 One horse power drives 500 on the fine hand-mule, 300 on the self-actor mule.1892Pall Mall Gaz. 24 Aug. 2/1 Fine spinning, for which self-actors cannot as yet be profitably introduced.