A person crosses their arms to form an "X" and places it in front of their body to show a "no" symbol. Gender does not matter as far as this emoji is concerned, but most versions of it are still female. The meaning of an emoji is determined by its gesture. It is always associated with disapproval, disagreement, prohibition, etc.
For example, it can be used as a negative answer to any question. It can indicate a reaction to something unpleasant. Finally, it may symbolize a negative attitude towards some activity.
Person Gesturing No was approved as part of Unicode 6.0 in 2010 under the name “Face with No Good Gesture” and added to Emoji 1.0 in 2015.
? Previously displayed a gendered appearance, now shown as gender neutral on most platforms.
U+1F645
? Face with no good gesture