Final answer:
The word 'agitation' contextually refers to a state of nervousness, restlessness, or emotional disturbance as exhibited by characters in various situations.
Step-by-step explanation:
The meaning of the word agitation in the context of the sentences provided suggests a state of nervousness or unrest. In the various examples, the characters exhibit signs of restlessness, irritability, and a sense of disturbance either due to the strain of legal matters, the influence of alcohol, a natural propensity towards nervousness, or emotional distress. Particularly in the sentence 'A startlingly swift change in the nature of her agitation made him reproach himself for his abruptness,' it implies a sudden increase in anxiety or emotional disturbance.