The word "lumboiliac" contains four syllables and is pronounced as /lʌm.bo.ɪl.i.æk/. The first syllable is stressed and contains the vowel sound /ʌ/. The next syllable includes the consonant blend /mb/, followed by the vowel sound /o/. The third syllable also contains a consonant blend /il/ and a vowel sound /i/. Finally, the last two syllables include the consonant sounds /i/ and /æk/ respectively. Overall, the spelling of "lumboiliac" accurately represents its pronunciation.
Lumboinguinal.
A practical medical dictionary. By Stedman, Thomas Lathrop. Published 1920.