From Latin prandium. Compare Italian pranzo, Aromanian prãndzu.
prânz n (plural prânzuri)
Ce vrei să mănânci la prânz mai târziu?
What do you want to eat for lunch later?
2) noon, midday
From Wiktionary: https://en.wiktionary.org/wiki/pr%C3%A2nz
pranzul = the lunch?
Is there a word without "-ul" since lunch isn't really something you'd say with "the" in front?
There are sentences where nouns do not have articles; for instance after the preposition "la" you often do not use an article. Nevertheless, Romanian generally uses the definite article more often than English.
Same as in Italian: "io mangio IL pranzo" (I eat the lunch), where pranzo is a noun; you can't say "io magio pranzo". If you don't want to use the article, then you have to omit the verb "mangiare", hence "io pranzo" (I lunch). Pranzo becomes then a verb (pranzare).
"Mangio" looks like "mange" from French. What a nice language family we all share. By the way, after I finish French, Romanian, and German, Italian is next as my 7th language (holy smokes!). It's a beautiful language.
Mic dejun = breakfast Dejun = lunch, but I have never heard anyone using it.
Dejun c'est comment en français, mais prânz c'est comment en italien. Très particulier!