over
They talked it over over dinner.
The sentence describes discussing a topic during a meal — first 'over' as part of the phrasal verb 'talk over' (to discuss), then as a preposition meaning 'during'.

Meanings (pronounced /ˈoʊvər/)
the second element of phrasal verbs like 'talk over' (discuss), 'go over' (review), 'think over' (consider)
- Let's talk it over later.
- I'll think the proposal over and get back to you.
while engaged in or consuming; in the course of
- We met over coffee.
- They negotiated over lunch.
Word origin
From Old English ofer ('above, beyond, on top of'), from Proto-Germanic *uberi, from Proto-Indo-European *upér ('over, above'). The same root underlies Latin super, Greek hyper, and Sanskrit upari. 'Over' is one of the most flexible English particles, working as preposition, adverb, prefix (overcome, overdo), and even noun (cricket's 'over').
Fun fact
'Over' is one of English's most overloaded function words — it can mean above (over the bridge), more than (over a hundred), during (over dinner), about (talk over the issue), finished (the game is over), and a dozen other things. Each use is a slightly different metaphor extending from the original spatial 'above' meaning.