how to pronounce the word "cataclysm" in both American and British accent?
We pronounce it as /0kæ tə 1klɪz əm/ in IPA.
Main stress occurs on the 1st syllable; secondary stress is on the 3rd. The consonant c after a is uttered as a hard sound, i.e. /k/ which usually is the phonics rule. The 1st vowel a is the ash æ (the short sound of a). The 2nd a in the 2nd syllable is reduced to a schwa ə after t. The l blend cl is pronounced as /kl/. The y in the 3rd syllable is uttered as a short i (/ɪ/) in a closed syllable and the sibilant s is usually voiced in sm(/z/). The m may be syllabic or uttered with a schwa in front of it /əm/.