[trey-ser] 
| 1. | a person or thing that traces. |
| 2. | a person whose business or work is the tracing of missing property, parcels, persons, etc. |
| 3. | an inquiry sent from point to point to trace a missing shipment, parcel, or the like, as in a transportation system. |
| 4. | any of various devices for tracing drawings, plans, etc. |
| 5. | Also called tracer ammunition. ammunition containing a chemical substance that causes a projectile to trail smoke or fire so as to make its path visible and indicate a target to other firers, esp. at night. |
| 6. | the chemical substance contained in such ammunition. |
| 7. | a substance, esp. a radioactive one, traced through a biological, chemical, or physical system in order to study the system. |
tracer trac·er (trā'sər)
n.
A substance, such as a dye or a radioactive isotope, that is introduced into and followed through a biological or chemical process, by virtue of its radioactive signature, color, or other distinguishing physical property, thus providing information on the course of the process or on the components or events involved.
An instrument used in dissecting out nerves and blood vessels.
sər