a single layer of cells growing on a cell culture surface
a single molecular layer of molecules at an interface
Tissue culture consisting of a single layer of cells.
arrangement of cells in a single layer (two-dimensional)
monomolecular film e.g. an adsorbate film of one molecule thickness, spread on a liquid or solid surface
A monolayer is a single, closely packed layer of atoms, molecules, or cells. http://www.iupac.org/goldbook/M04015.pdf.