The Collaborative International Dictionary
Intracellular \In`tra*cel"lu*lar\, a. (Biol.) Within a cell; as, the intracellular movements seen in the pigment cells, the salivary cells, and in the protoplasm of some vegetable cells; intracellular enzymes. Contrasted with extracellular.
Douglas Harper's Etymology Dictionary
Wiktionary
a. Inside or within a cell.
WordNet
adj. located or occurring within a cell or cells; "intracellular fluid" [ant: extracellular]
Wikipedia
In cell biology, molecular biology and related fields, the word intracellular means "inside the cell".
It is used in contrast to extracellular (outside the cell). The cell membrane (and, in many organisms, the cell wall) is the barrier between the two, and chemical composition of intra- and extracellular milieu ( Milieu intérieur) can be radically different. In most organisms, for example, a Na+/K+ ATPase maintains a high potassium level inside cells while keeping sodium low, leading to chemical excitability. This terms also means existing within the cells.
Usage examples of "intracellular".
They can be measured biochemically, in terms of a cellular cascade of processes which begins with the opening of ion channels in the synaptic membranes and proceeds by way of complex intracellular signals to the synthesis of new proteins which, inserted into the synaptic and dendritic membranes, are responsible for these morphological changes.
The man said its cells were saturated with neurophysin proteins, intracellular carriers, but of an unknown type.
Reading the descriptions on the back of each photo, Jeffrey learned that the electron micrographs showed marked destruction of the intracellular architecture.
Anyway, basically, what a lab is going to be looking for is whether that hyperpigmentation is intracellular, as in melanocytes, which are the dark, pigmented cells that are much more concentrated in non-Caucasians, or intercellular.
Potassium ion, in contrast, is found almost entirely within the cells in the intracellular fluid.