Final answer:
The phrase "imprisoned by the waves" best implies that 'thwart' means to prevent or obstruct something, as the waves are impeding Daedalus's return home.
Step-by-step explanation:
The phrase that provides the best clue to the meaning of the word "thwart" in the given passage is "imprisoned by the waves". This suggests that Daedalus's efforts are being obstructed or prevented by the sea, which is the essence of the word "thwart".
The sea is metaphorically acting as a barrier to Daedalus's desire to return home, and he recognizes that Minos, the ruler of Crete, has no power to stop them if they travel through the sky, which is why they consider escape by air.
Some common synonyms of thwart are baffle, balk, foil, and frustrate. While all these words mean "to check or defeat another's plan or block achievement of a goal," thwart suggests frustration or checking by crossing or opposing. the army thwarted his attempt at a coup.