radioactive substance attached to another: a radioactive substance attached to another substance as a means of tracing the location or tracking the movement of that substance. The technique is used in medicine, e.g. to monitor the distribution of a drug throughout the body.
transitive verb (past and past participlera·di·o·la·beled or ra·di·o·la·belled, present participlera·di·o·la·bel·ing or ra·di·o·la·bel·ling, 3rd person present singularra·di·o·la·bels)
Definition:
tag substance with radiolabel: to attach a radiolabel to a substance