"Silk reeling" - the name refers to any of a large number of exercises in which the object is to move your hands in a repeating pattern very evenly, with no jerking or variation in speed.
The name comes from literally reeling silk off the cocoons of silkworms, a task traditionally done by young girls. If you pull too hard or unevenly, the silk thread breaks. Short silk threads were worth much less than long ones, so the movement must be done very smooth and evenly, same as in Tai Chi.
Silk Reeling is a distinct feature of Wudang Tai Chi and Chen Style Tai Chi, referring to continuous rounded and spiral movements utilising the whole body and limbs on top of the regular move from point A to point B.
Basically it means that power does not transfer in a linear fashion but it coils and spirals along the limbs. Thus there are two directions (clockwise & anti-clockwise).