What is the meaning of Nodus?

A difficulty.

In the Odonata, a prominent crossvein near the centre of the leading edge of a wing.

articulation: a joint between two separable parts, as a leaf and a stem

node: a small mass of tissue that can be a knot, knob, or swelling

a knot (in rope)

a knot (in wood)

a knob

a bond

an obligation

a sticking point

a knotted fishing net

Source: wiktionary.org