Combination of the Tagalog words almusal (breakfast), tanghalian (lunch), and hapunan (dinner).
Also spelled with hyphens as al-tang-hap.
This is not a word that can be found in standard dictionaries.
Altanghap refers to the single daily meal that poor Filipinos eat, usually at noon. It often doesn’t even involve rice, which is expensive compared to, for example, bananas.
Even if one can afford rice, there is no traditional ulam (entree like fish or meat) to pair with the boiled rice. Instead, one eats the steamed rice plain or with some salt or sugar.
One can imagine that Manny Pacquiao during his poverty as a child would eat only once a day. His family was so poor they could not afford rice and had to subsist on boiled root crops, like sweet potatoes probably.
The reason for eating altanghap is of course not limited to having no money to buy substantial food. Sometimes, people are so busy that they do end up eating just once a day.
A recent lifestyle trend among health-conscious Americans is to follow the OMAD diet. OMAD stands for “One Meal a Day.” This is reportedly good for longevity.