Synonyms and related words :
Cassandra, Eeyore, calamity howler, crepehanger, cynic, damp, dampener, damper, defeatist, gloomy Gus, grouch, grump, malcontent, malist, negativist, nihilist, pessimist, prophet of doom, retreatist, seek-sorrow, sourpuss, spoilsport, wet blanket, worrywart