For the purpose of these Rules, except where the context otherwise requires:
- (a)'Vessel' includes every description of water craft, including non-displacement craft, WIG craft and seaplanes, used as a means of transportation on water.
- (b)'Power-driven vessel' means any vessel propelled by machinery.
- (c)'Sailing vessel' means any vessel under sail, provided that propelling machinery, if fitted, is not being used.
- (d)'Vessel engaged in fishing' means any vessel fishing with nets, lines, trawls or other apparatus which restrict manoeuvrability, but not trolling lines.
- (e)'Seaplane' includes any aircraft designed to manoeuvre on the water.
- (f)'Vessel not under command (NUC)' means a vessel which through some exceptional circumstance is unable to manoeuvre as required.
- (g)'Vessel restricted in her ability to manoeuvre (RAM)' means a vessel which from the nature of her work is restricted in her ability to manoeuvre.
- (h)'Vessel constrained by her draught' means a power-driven vessel severely restricted by her draught.
- (i)'Underway' means not at anchor, made fast to the shore, or aground.
- (j)'Length' and 'breadth' of a vessel mean her length overall and greatest breadth.
- (k)Vessels are 'in sight of one another' only when one can be observed visually from the other.
- (l)'Restricted visibility' means any condition in which visibility is restricted by fog, mist, falling snow, heavy rain, sandstorm or any similar cause.
- (m)'WIG craft' means a multimodal craft which, in its main operational mode, flies in close proximity to the surface using surface-effect action.