AU BESOIN. This is a French phrase, used in commercial law. When the drawer of a foreign bill of exchange wishes as a matter of precaution, and to-save expenses, he puts in the corner of the bill, " Au besoin chez Messieurs or, in other words, " In case of need, apply to Messrs. at __________ " ___________." 1 Bouv. Inst. n. 1133 Pardess Droit Com. 208.