Student or Learner
"He doesn't really mean what he's saying. He's only making a gesture."
What does it mean of "He's only making a gesture"?
A gesture can be an actual movement meant to emphasize or replace speech ("Sit down," she said, gesturing towards the armchair") or it can be an act that shows attitude ("The ambassador visited the new embassy as a goodwill gesture").
The word is often used with the adjective "empty," meaning that the gesture is not sincere. In this case, even without an adjective, the speaker means that the subject of the sentence is not sincere.
[native speaker, not a teacher]