The spelling of the word "OSISD" can be explained using the International Phonetic Alphabet (IPA). The first letter "O" is pronounced as "ɔ", similar to the "a" sound in "bought". The following "S" is pronounced as "s", which is an unvoiced consonant sound. The letters "I" and "D" are pronounced as "ɪ" and "d" respectively. The final letter "S" is again pronounced as the unvoiced consonant sound "s". Thus, the correct pronunciation of "OSISD" would be "ɔsɪsd".