The Collaborative International Dictionary
Leucoplastid
Leucoplast \Leu"co*plast\ (l[=u]"k[-o]*pl[a^]st), Leucoplastid \Leu`co*plas"tid\ (-pl[a^]s"t[i^]d), n. [Leuco- + Gr. pla`ssein to mold.] (Bot.) One of certain very minute whitish or colorless granules occurring in the protoplasm of plants and supposed to be the nuclei around which starch granules will form.
Wiktionary
leucoplastid
n. (context biology English) A kind of unpigmented plastid involved in a wide range of essential biosynthetic functions.