Questions & Answers about Он пожал плечами и ничего не сказал.
Why is it пожал плечами and not something like пожал плечи?
Because the verb пожать / пожимать плечами is a fixed expression meaning to shrug. With this expression, плечами is in the instrumental plural.
So Russian treats it roughly like to move/shake with the shoulders, not to shrug the shoulders in the direct-object sense English uses.
- плечи = shoulders
- плечами = with the shoulders / by means of the shoulders
This is just the normal case pattern for this idiom:
- Он пожал плечами. = He shrugged.
- Она только пожала плечами. = She only shrugged.
What exactly does пожал mean here?
Пожал is the masculine past tense singular form of пожать, which is a perfective verb.
In this sentence, пожал плечами means shrugged.
A useful thing to know is that пожать has more than one meaning depending on context:
- пожать руку = to shake someone’s hand
- пожать плечами = to shrug
- пожать can also mean to reap/harvest in other contexts
So here you understand the meaning from the object and idiom:
- пожал плечами = shrugged