Final answer:
Columbia is referred to as the "Guardian of the ocean" in patriotic songs, symbolizing the protective role of the United States.
Step-by-step explanation:
In patriotic songs, Columbia is referred to as the "Guardian of the ocean." This epithet is used to symbolize the protective and nurturing role of Columbia, which is often portrayed as a personification of the United States.
One example of this reference can be found in the poem "On the Nature of Things" by Lucretius, where Columbia is described as the "guard and glory of their parents' years."