Definition of heliotropes:
(n) :
(specifically) A plant of the genus Heliotropium, especially the common heliotrope (Heliotropium arborescens) which has clusters of purple flowers with a strong fragrance.
(n) :
(uncountable) The fragrance of Heliotropium arborescens flowers, or a scent resembling this fragrance.
(n) :
(uncountable) A light purple or violet colour like that of Heliotropium arborescens flowers.
(n) :
(countable) An instrument that uses a mirror to reflect sunlight for purposes such as signalling, or (surveying) triangulation (where the reflected light is detected by another surveyor positioned some distance away).
(n) :
With a qualifying word: any of various plants resembling those of the genus Heliotropium.
(n) :
(countable, botany, also figuratively) A plant with flowers which turn to face and follow the sun, such as (archaic) marigolds and sunflowers.