No it's not, neither is grasping or clamping the opponent under the shoulder pads.
NCAA[edit]
The following is quoted directly from the NCAA 2015 Rules and Interpretations document available online
here
Holding[edit]
Illegal use of the hand or arm is unfair play, eliminates skill and does not belong in the game. The object of the game is to advance the ball by strategy, skill and speed without illegally holding your opponent. All coaches and players should thoroughly understand the rules for proper offensive and defensive use of the hands. Holding is a frequently called penalty; it is important to emphasize the severity of the penalty. [1]Holding and Use of Hands or Arms: Offense[edit]
ARTICLE 3.
a. Use of Hands
A teammate of a ball carrier or a passer legally may block with his shoulders, his hands, the outer surface of his arms or any other part of his body under the following provisions.
1. The hand(s) shall be:(a) In advance of the elbow.(b) Inside the frame of the opponent’s body (Exception: When the opponent turns his back to the blocker) (A.R. 9-3-3-VI and VII).(c) At or below the shoulder(s) of the blocker and the opponent (Exception: When the opponent squats, ducks or submarines).(d) Apart and never in a locked position.
2. The hand(s) shall be open with the palm(s) facing the frame of the opponent or closed or cupped with the palms not facing the opponent (A.R. 9-3-3-I-IV and VI-VIII). RULE 9 / CONDUCT OF PLAYERS AND OTHERS SUBJECT TO THE RULES FR-97
b. Holding
The hand(s) and arm(s) shall not be used to grasp, pull, hook, clamp or encircle in any way that illegally impedes or illegally obstructs an opponent.
PENALTY—10 yards Penalties for Team A fouls behind the neutral zone are enforced from the previous spot. Safety if the foul occurs behind Team A’s goal line [S42].
Holding (American football) - Wikipedia