A micro-gesture (microgesture) is a gesture that is created from a defined user action that uses small variations in configuration, or micro-motions. In the most general sense, micro-gestures can be described as micro-interactions. Being that micro-gestures use small variations in configuration and motion, gesture actions can be achieved with significantly less energy than typical touch, motion or sensor-enabled gestures. This has great benefits for users as it allows effortless interactions to occur in rapid succession which directly supports greater fidelity and productivity within natural user interfaces.
Is a definition for «micro-gesture» found on http://www.gestureml.org/doku.php/gestures/fusion/microgesture_index.
I want to highlight the point that micro-gestures are very easy to perform and I want to add that they also have the advantage of being very unobtrusive.