The word "mayonnaise" is pronounced as:

• In English: /ˌmeɪ.əˈneɪz/
  Sounds like: may-uh-NAYZ

If you want to say it in other languages:

• French (origin): mayonnaise — pronounced mah-yoh-NEHZ
• Spanish: mayonesa — pronounced mah-yoh-NEH-sah
• German: Mayonnaise — pronounced mai-oh-NEH-zuh

Would you like the pronunciation in a specific language or phonetic spelling?