What does "molecular" mean?

Molecular: Pertaining to, connected with, produced by, or consisting of, molecules; as, molecular forces; molecular groups of atoms, etc. Molecular attraction (Phys.), attraction acting between the molecules of bodies, and at insensible distances. -- Molecular weight (Chem.), the weight of a molecule of any gas or vapor as compared with the hydrogen atom as a standard; the sum of the atomic weights of the constituents of a molecule; thus, the molecular weight of water (H2O) is 18.