Hindu is definitely listed as vegetarian in the description on UA. Unless that changed, recently.

Not sure about other carriers in the US, but at least most Asian carriers have an Asian Vegetarian (think its usually Chinese-style), Indian Vegetarian (which, based on the description, is what UA calls Hindu), and separately, a Hindu meal which (IIRC) is meat that is Halal (or fish), but definitely no pork/beef, and I think pretty much always Indian-style.

The important thing I think is what IATA meal codes the UA-marketed meal types link up to - I would assume an agent can see that, but those are definitely standards across the industry.