Final answer:
The term 'firmly gripped' refers to grabbing something very tightly, ensuring a secure and strong hold.
Step-by-step explanation:
The word that means grabbing very tightly can be described as firmly gripped. When someone firmly grips an object, their hand is making a tight and secure hold on the object, as opposed to being loosely held. In the context provided, when the character Alcée's arm encircles Calixta and he draws her close spasmodically to him, it indicates that he is holding her very tightly, illustrating a firm grip.