The twelve principles of animation
Also said as Twelve basic principles, Disney's principles
Twelve rules for making drawings seem alive, worked out by Disney's animators and set down by Frank Thomas and Ollie Johnston in their 1981 book The Illusion of Life. They are still how animators talk about motion.
They name what is missing when a thing moves correctly and still looks dead. Nearly all "it feels stiff" notes are one of these twelve.
Say it
“The boss looks stiff. Apply the principles: half a second of anticipation before the slam, slow in and slow out on the arm, an arc on the swing, and follow-through on the cape.”
Where you’ve seen it
Cuphead, drawn by hand to match 1930s cartoons, shows them openly: nearly everything on screen squashes, stretches, anticipates and overshoots.
Not to be confused with game feel
The principles describe how motion looks. Game feel also covers how it answers your hands. A long anticipation can be a great animation and a terrible control.