adj. Of or pertaining to thallium, especially to thallium having an valency of 1
the GNU version of the Collaborative International Dictionary of English
adj. Of or pertaining to thallium; derived from, or containing, thallium; specifically, designating those compounds in which the element has a lower valence as contrasted with the thallic compounds.
Word Usage
"In February, 2007, I took a treadmill stress test during which thallous chloride was injected into my bloodstream."