To me, communication is a much overlooked part of engineering. As I've advised my children (both engineers), no matter how good your ideas and solutions are, you need to be able to explain them clearly and "sell" them to others, so they will implement them.
Also be genuinely open to other's ideas (acting interested), and be able to explain why you agree or disagree without making it personal. If you agree with part of their ideas, work them into yours and show you are a team player. This makes it easier for them to contribute in the future, without worrying about being ignored or ridiculed.
So I guess that, besides being clear and correct, communication means establishing mutual respect.