1lunch 
/ˈlʌntʃ/ noun
plural lunch·es /ˈlʌntʃ/ noun : a light meal eaten in the middle of the day [count] ▪ I like to eat/have a healthy lunch every day. ▪ a company lunch [=luncheon] ▪ We took a picnic lunch to the park. ▪ They've brought their own lunches with them. ▪ We discussed the idea over a working/business lunch. [=a lunch during which people talk about business matters] [noncount] ▪ What's for lunch? ▪ I had/ate just a sandwich for lunch. ▪ Where do you want to go for lunch? = Where do you want to eat/have lunch? ▪ I bought her some lunch. ▪ She often sits alone at lunch. [=while eating lunch] ▪ We discussed the idea over lunch. [=during lunch; while eating lunch] ▪ I offered to take her out to lunch. [=to take her to a restaurant for lunch] ▪ lunch hour [=the time when the people in a school or company eat lunch] ◊When people do lunch they have lunch together. This is an informal phrase that is often associated with people in business.
▪ Let's do lunch sometime.
▪ Let's do lunch sometime.
eat/have someone or something for lunch or eat someone's or something's lunch
US, informal : to defeat someone or something very badly
▪ The big hardware chain was eating the local store's lunch. [=the big chain was taking a lot of business from the local store]
▪ The big hardware chain was eating the local store's lunch. [=the big chain was taking a lot of business from the local store]
lose your lunch
no free lunch
◊The expression there is no free lunch or there is no such thing as a free lunch means that it is not possible to get something that is desired or valuable without having to pay for it in some way.
out to lunch
informal : not aware of what is really happening : too strange or confused to notice or understand what is really happening
▪ That guy acts like he's out to lunch.
▪ That guy acts like he's out to lunch.
