There was actually a loosely related thread about this kinda stuff two weeks ago...in anycase, here are the caveats that were shared in that thread. I've written the meal codes here but I understand that these codes can be different from airline to airline and not airlines have all these meals available.
HVML - Hindu Vegetarian - While most people would think that this meal would mean NO MEAT, some airlines (AF in particular) believe that fish and seafood in general are "vegetarian." You have to check with your individual airline as some people (who have no brains) think that the Hindu diet is one that allows all sorts of meat except beef and/or pork. Hindus who've ordered this meal have ended-up with fish and shrimp on their plate...NOT their cup o tea.
AVML - Asian Vegetarian - This one varies from airline to airline. On SQ
this actually equates to Indian vegetarian (which you think would be Hindu vegetarian). On most airlines that I've flown, you get an Indian-like meal. On some airlines, this equates to more Asian dishes with bean curd (tofu) and vegetables.
VLML - Ovo-Lacto Vegetarian - Eggs and milk vegetarian. I haven't flown UA
lately, but a long time ago when I flew DL
and ordered the VLML meal, we got a VERY TASTY mac and cheese and a side of broccoli. Many times, however, the kitchen gets lazy and they end-up giving you a strict vegetarian meal even when you order VLML.
VGML - Strict Vegetarian Meal - No milk, eggs, pork, beef, or seafood. Basically, by ordering this meal, you're eating all vegetable, bread, and rice items. These dishes are normally very bland. Occasionally, they'll substitute (not so) fresh fruit in place of the cakes and cookies everybody else is enjoying. The salad dressing is usually oil-based and quite distasteful.
That's all I have to share. Hope you have a good experience.
You land a million planes safely, then you have one little mid-air and you never hear the end of it - Pushing Tin