In shaving parlance, hysteresis is that which supposedly makes two blades better than one.

When shaving with a multiple-blade razor, the first blade cuts into the whisker while simultaneously pulling it out slightly. Before it can retract, subsequent blades cut the hair even closer, resulting in whiskers which end up below the surface of the skin.

According to Cecil Adams of The Straight Dope, Gillette claims to have slow-motion microphotography demonstrating hysteresis.

Sources:

The Gillette Company Web Site:
http://www.gillette.com

The Straight Dope:
http://www.straightdope.com

Hys`te*re"sis (?), n. [NL., fr. Gr. to be behind, to lag.] Physics

A lagging or retardation of the effect, when the forces acting upon a body are changed, as if from velocity or internal friction; a temporary resistance to change from a condition previously induced, observed in magnetism, thermoelectricity, etc., on reversal of polarity.

 

© Webster 1913.

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