Vex·il·lar Vex·il·la·ry
1. Of or pertaining to an ensign or standard.
2. Bot. Of or pertaining to the vexillum, or upper petal of papilionaceous flowers.
Vexilary aestivation Bot., a mode of aestivation in which one large upper petal folds over, and covers, the other smaller petals, as in most papilionaceous plants.