1. noun Literally, a whistle that emits sound at a frequency so high that it can be heard by dogs but not humans. The dogs all started howling at the sound of the trainer's dog whistle.

2. noun By extension, a word or phrase specifically used to convey an innocuouss meaning to the general audience while conveying or suggesting a different, often controversial, message to the target audience. Especially used in politics. He's using that term as a dog whistle to signal to his base what his values really are.

3. noun The tactic of using such a term. His use of the term is clearly a dog whistle intended to rally his base.

4. adjective Describing such a term or tactic. When used as an adjective, the phrase is commonly hyphenated. Allusions to issues like race are commonly couched in dog-whistle terms to appeal to certain blocs of voters while going unnoticed by others.