Fidelitous is a rarely used adjective which means being faithful or loyal. The spelling of this word can be challenging to master without the proper knowledge of phonetics. The word is pronounced as fahy-del-i-tuhs with the stress on the second syllable. The first syllable is pronounced with the long "i" sound supported by the vowel "e". The last syllable is pronounced with a short "u" sound along with the letters "s" and "t" that give the word its proper ending sound.