What is Going Before The Wind?

Legal Definition
In the language of mariners and in the rules of navigation, a vessel is said to be going "before the wind" when the wind is free as respecte her course, that is, comes from behind the vessel or over the stern, so that her yards may be braced square across. She is said to "going off large" when she has the wind free on either tack, that is, when it blows from some point abaft the beam or from the quarter. Hall v. The Buffalo, 11 Fed. Cas. 216; Ward v. The Fashion, 29 Fed. Cas. 188.
-- Black's Law Dictionary