1) Complication 2) Difficult point 3) Difficult situation 4) Difficulty 5) Knotty situation 6) Knotty spot 
(of Odonata ) A prominent cross-vein near the center of the leading edge of a wing.
Strong cross vein near middle of costal border of wing
a knotty point; difficulty; complication
The kink or notch on the costal margin of the dragonfly wing
Synonym: node. ... Origin: L. A knot ... (05 Mar 2000) ... 
(no´dәs) Latin word meaning node; a term used in anatomy.
The kink or notch on the costal margin of the dragonfly wing
Type: Term Pronunciation: nō′dŭs, -dī Synonyms: node
nodus (s), nodi (pl) 1. A node or knot; used in anatomical nomenclature as a general term to designate a small mass of tissue. 2. A difficulty; a complexity, or a knotty point.
a difficult or intricate point, situation, plot, etc.