A sly dog informal noun
A tricky or dishonest person
Stay away from him. He's a sly dog.
What a sly dog! He cheated my money.
To deceive or trick someone
1. To carry out something foolish or risky
2. To carry out a trick
To do domething based on your emotions rather than for rational reasons
I can't believe that Tom beat his classmate. He's always the one who let his heart rule his head.