D defs.my
Entry 2 senses Webster, 1913

Strontium

/strŏn'tēəm/ · Stron·ti·um · IPA /ˈstɹɒn.ti.əm/
01 n. A metallic element of the calcium group, always naturally occurring combined, as in the minerals strontianite, celestite, etc. It is isolat…
  1. 1.
    A metallic element of the calcium group, always naturally occurring combined, as in the minerals strontianite, celestite, etc. It is isolated as a yellowish metal, somewhat malleable but harder than calcium. It is chiefly employed (as in the nitrate) to color pyrotechnic flames red. Symbol Sr. Atomic weight 87.3.(Chem.)
  2. 2.
    A radioactive isotope of strontium produced by certain nuclear reactions, and constituting one of the prominent harmful components of radioactive fallout from nuclear explosions; also called radiostrontium. It has a half-life of 28 years. Also: radiostrontium