If quiver means "to tremble or shake":
* Steady: This is the most general opposite, meaning to be firm and not shake.
* Unwavering: This emphasizes the lack of any shaking or hesitation.
* Calm: This implies a state of peace and tranquility.
* Still: This means being motionless and without movement.
If quiver means "a case for holding arrows":
* Bow: This is the weapon that the arrows are used with.
* Quiver full: This is a specific state of having arrows ready, rather than an opposite.
If quiver means "a feeling of excitement or nervousness":
* Calm: This implies a state of peace and relaxation.
* Composure: This indicates a state of being collected and self-assured.
* Confidence: This suggests a belief in oneself and one's abilities.
Therefore, the best opposite for "quiver" depends on the specific meaning you want to convey.