For example, in this sentence:

Milk doesn't sit well with me before or after tough workouts.

And also I like to know synonyms for this idiom.

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  • It would be helpful to tell us what your research has turned up on the phrase and to post that research. (Further, your title asks for an exact meaning, while your question asks for an idiom. Did you want both?) – rajah9 Jun 29 '15 at 15:35
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    Idiomatically it's almost always sit well with me (1130 hits in Google Books), not sit with me well (36 hits). A very common alternative for food/drink your body reacts against is doesn't agree with me. – FumbleFingers Jun 29 '15 at 15:38

To not "sit well with" as an idiom meaning that a situation is difficult to agree with or to accept. See not sit well at the Free Dictionary. Their example:

The idea of declaring war does not sit well with many voters.

If X is a food or beverage that "doesn't sit with me well," it means that X does not agree with (or is not accepted by) my digestive system. This might mean gas, nausea, vomiting, or diarrhea.

Idioms are

Milk does not agree with me.

Other words are:

Milk upsets my stomach.

Milk gives me a stomach ache.

  • @Soudabeh It's a metaphor. – Barmar Jun 29 '15 at 16:02
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    To "not sit well" is always idiomatic, as it never refers to how something is sitting. Milk or another beverage can never sit. Neither can a situation be placed into a seated position. When someone says a food or drink does not sit well, they are substituting a euphemism for an explicit word like gas, nausea, vomiting, or diarrhea. It is more indirect and polite to say to a host, "Milk does not sit well with me" or "Milk does not agree" with me instead of "Milk makes me vomit." – rajah9 Jun 29 '15 at 16:05
  • @Soudabeh "Not sit well" is the idiom, applying it to food is just a particular usage of that idiom. – Chris Sunami Jun 29 '15 at 16:05
  • @Soudabeh If you want to send a comment to someone, don't put "Dear" before "@". And make use of the auto-complete, so the name is spelled correctly automatically. – Barmar Jun 29 '15 at 16:08
  • @ChrisSunami If I recall correctly, I've heard the words "does not sit well on" used somewhat lexically to refer to how well something is balanced or stabilized or attached something else is on top of another before. I can't cite any authoritative sources right now but here's an Amazon review using the word that way in regards to the compatibility of toys. – Tonepoet Jul 30 '15 at 18:31

It's an idiom indicating that it disagrees with him. In this sense, this definition of "disagree" from Noah Webster's 1828 American Dictionary of the English Language probably applies:

  1. To be unsuitable. Medicine sometimes disagrees with the patient; food often disagrees with the stomach or the taste.

It does not suit him to drink milk after a workout. This is most probably because it makes him feel somehow ill. Most often it refers to a stomach ache but other reasons may apply, for instance perhaps it makes him feel fatigued and dizzy or maybe he just finds it tastes bad for some unspecified reason.

Cambridge Dictionary of American Idioms. S.v. "not sit well." Retrieved from The Free Dictionary by Farlex.

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