To make movements with your hands or arms, to express something or to emphasise what you are saying. (Cambridge Dictionary)
If you gesticulate, you make movements with your arms or hands, often while you are describing something that is difficult to express in words. (Collins Dictionary)
To make gestures especially when speaking. (Merriam – Webster)
Use gestures, especially dramatic ones, instead of speaking or to emphasise one’s words. (Oxford Dictionaries)
Meaning of gesticulate. Word pandit.