“Tipping pitches” is a term used to describe actions by a pitcher that unwittingly reveals to opponents which pitches he plans to throw. That disclosure can come in the form of a change in stance, grip, or demeanor before certain pitches, unusual (for him) mannerisms or ticks only before particular pitch types, or other “tells” that accompany his pitch selections.
While it is illegal to “steal” signs in baseball, there is little that a team can do to prevent opposing batters to using the information they glean from tipped pitches to their advantage.
After all, stealing signs usually involves a coach or other player telegraphing pitches called by the opposing catcher to the batter, while the batter himself has the opportunity to interpret a pitcher’s body language, and to react accordingly in terms of pitch anticipation.
The best defense a team has against a hurler tipping pitches is to recognize it as early as possible and then work to change the mannerisms involved.
In terms of body language and motion on the mound, a pitcher‘s goal should be to present the same “look” to each batter, no matter what the circumstance or what pitch he’s planning to deliver.