Synonyms for Cowslip (same or very similar meaning)
WordNet sense 1 (early spring flower common in British isles having fragrant yellow or sometimes purple flowers):
paigle, Primula verisWordNet sense 2 (swamp plant of Europe and North America having bright yellow flowers resembling buttercups):
kingcup, marsh marigold, Caltha palustris, May blob, meadow bright, water dragonFrom the ODE community, based on WordNetadd/edit