call for water - If a boat with the right of way is forcing you into the shore, you can tell her to get out of the way.

clear ahead - When no part of the boat mostly behind you is beside you.

Clear Astern and Clear Ahead - Overlap  One boat is clear astern of another when her hull and equipment in normal position are behind a line abeam from the aftermost point on the other boat’s hull and euipment in normal position.  The other boat is clear ahead.  They overlap when neither is clear ahead.  However, they also overlap when a boat between the overlaps both.  These terms always apply to boats on the same tack.  They do not apply to boats on opposite tacks unless rule 18 applies or both boats are sailing more than ninety degrees from the true wind. (ISAF Rules)

clew - the back lower corner of the sail.

close hauled - having the sails trimmed in as far as possible for maximum speed up wind.

close reach - sailing with the wind between coming from the side and from the front.

clove hitch - A knot often used to to attach a rope to to post

coming about - Turning the boat when the wind is coming from the front.

Cunningham - A rope used to pull the front, bottom corner (the tack) down, tightening the luff.

daggerboard - A foil (or board) inserted through the boat bottom to prevent the boat from sideslipping.  Usually you pull the daggerboard up when the running.

fall off - Same as bear off.

favored end of the line - The position on the starting line which provides the best chance of beating the other boats to the first mark.

Fetching - A boat is fetching a mark when she is in a position to pass to windward of it and leave it on the required side without changing tack. (ISAF Rules)

Finish - A boat finishes when any part of her hull, or crew or equipment in normal position, crosses the finish line in the direction of the course from the last mark, either for the first time or after taking a penalty  under rule 44.2 or, after correcting an error made a the finishing line, under rule 28.1. (ISAF Rules)

flying gybe - A gybe during which the boom goes from leeward to windward very rapidly.  Unless  held down by a vang, it sometimes flies up on its trip.

foot - The bottom edge of the sail