33 CFR § 84.01 - Definitions.
(a) The term height above the hull means height above the uppermost continuous deck. This height shall be measured from the position vertically beneath the location of the light.
(b) High-speed craft means a craft capable of maximum speed in meters per second (m/s) equal to or exceeding: 3.7▽ 0.1667; where ▽ = displacement corresponding to the design waterline (cubic meters).
The same formula expressed in pounds and knots is maximum speed in knots (kts) equal to exceeding 1.98 (lbs) 3.7▽ 0.1667; where ▽ = displacement corresponding to design waterline in pounds.
(c) The term practical cut-off means, for vessels 20 meters or more in length, 12.5 percent of the minimum luminous intensity (Table 84.14(b)) corresponding to the greatest range of visibility for which the requirements of Annex I (33 CFR part 84) are met.
(d) The term Rule or Rules has the same meaning as in 33 CFR 83.03(r).