Definitions of shallow:

• noun:   a stretch of shallow water
• verb:   become shallow

  Example: "The lake shallowed over time"

• verb:   make shallow

  Example: "The silt shallowed the canal"

• adjective:   lacking depth of intellect or knowledge; concerned only with what is obvious

  Example: "Shallow people"

• adjective:   lacking physical depth; having little spatial extension downward or inward from an outer surface or backward or outward from a center

  Example: "Shallow water"

• adjective:   not deep or strong; not affecting one deeply

  Example: "Shallow breathing"

• name:  A surname (very rare: popularity rank in the U.S.: #45461)