A biology term, sometimes specifically applied only to animals -- when this is the case, the equivalent term for plants is monocarpic. Contrast with iteroparous, reproducing multiple times during a lifetime (or poloycarpic for plants). Examples of semelparous animals include salmon, who swim upstream to spawn in fresh water and then die, and many insects -- it's rare in cordates outside of fish. From Latin roots Latin semel, once + -parous, birth-related; iteroparous is from iterō, I do a second time, which also gave us iterate).
The semelparous century plant raised up its mast and unfurled its flowered booms to begin its first and final voyage.
(Not that there are any blooming agaves outside my window.)