A rule stating that an airplane designed with the same cross-sectional area distribution in the longitudinal direction as the Sears-Haack body generates the same wave drag as this body, largely independent of the actual shape; used in aerodynamics to reduce drag, typically by narrowing the fuselage at the wing roots.

(informal) Australian rules football.

plural of rule of thumb

(law) The unofficial acceptance of the use of one's spouse's private documents in court during a divorce.

(thermodynamics) An empirical rule stating that a linear relationship exists between the temperatures at which two solutions exert the same vapor pressure.

(in attributive usage) Alternative spelling of rule of thumb

The regulation requiring all traffic (travelling on a road or otherwise) to keep either to the left or the right. / (nautical) A regulation concerning safe handling of vessels on seaways.

plural of blood rule

(sports) A rule requiring that a player receive medical attention before continuing to play if he is bleeding or there is blood on him or his clothes.

(religion, Wicca) A religious tenet held by some Wiccans, stating that whatever energy, positive or negative, a person puts into the world will be returned threefold.