Sentence:  ‘I have a feeling that if we follow a scent of spring on the air with sufficient eagerness we'll come to a south without snow more quickly than we think. "Thalassa, thalassa". This is what the Greeks called an <WSD>anabasis</WSD>.' They looked at him as if he were barmy. 
Meaning of the word marked with <WSD> tags:  A military march up-country, especially that of Cyrus the Younger into Asia.