Lunch was a meal usually eaten at midday.
In 2364, Clare Raymond recalled that her beloved husband Donald Raymond may have had the best of intentions for cryogenically preserving her corpse on the SS Birdseye, but that he could mess up a free lunch. (TNG: "The Neutral Zone")
Dr. Julian Bashir and the Cardassian tailor Garak often ate lunch together at the Replimat on Deep Space 9. As of 2370, they had been meeting for about two years. (DS9: "Cardassians", "The Wire" et al.)
In 2373, Keiko O'Brien was injured when a Pah-wraith that was possessing her caused her to jump from the upper level of Deep Space 9's Promenade in order to impress upon Miles O'Brien the seriousness of the actions that it would take if he attempted to subvert its actions. When Miles was asked what he was doing on the Promenade when he was supposed to be repairing optronic circuitry on level five, he excused it by stating that he was going to the Replimat for lunch. (DS9: "The Assignment")
After being injured and having to wait for treatment after a Dominion attack on the USS Defiant in 2374, Garak told Dr. Bashir that he thought he was entitled to preferential treatment by him after all the lunches they had shared together. (DS9: "A Time to Stand")