'snow-in-summer' definitions:

noun

Annual spurge of western United States having showy white- bracted flower clusters and very poisonous milk [syn: snow-on-the-mountain, snow-in-summer, ghost weed, Euphorbia marginata]

noun

Chickweed with hairy silver-grey leaves and rather large white flowers [syn: snow-in-summer, love-in-a-mist, Cerastium tomentosum]