van der Waals force

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A weak attractive force between atoms or nonpolar molecules caused by a temporary change in dipole moment arising from a brief shift of orbital electrons to one side of one atom or molecule, creating a similar shift in adjacent atoms or molecules.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun chemistry, often in plural The relatively weak attraction between neutral atoms and molecules arising from polarization induced in each particle by the presence of other particles.