Shallow

Shallow means not very deep. It can be quite advantageous, e.g. a shallow pool is safe for swimming and a shallow ore is easy to mine.

Nonetheless, used metaphorically it is a derogative term used to describe people who are perceived to lack intellectual "depth". There is no standard definition of what constitutes "depth" in this sense, but usually an individual is considered deep if they seem to be interesting, original, creative, philosophical or intelligent. By contrast, somebody who appears superficial, naive, materialistic, petty, unimaginative or a conformist is likely to be denounced as being shallow, although simply lacking intelligence is not a criterion on its own.

Behaviors that are considered shallow
Shallow people typically embrace stereotyped social roles, especially gender roles. They usually place excessive value on the appearance of something, sometimes judging themselves and others entirely by their looks, which gives the impression of vanity and arrogance even though they may possess neither of these attributes.

Conversation with shallow people tends to remain on a very superficial level, often relating to the everyday details of their lives or the affairs of others; gossip is almost exclusively the domain of the shallow. This is not to suggest however that shallow people are malicious or vindictive; indeed they are often very positive and friendly in their outlook.

Though not malicious or vindictive, they tend to look to the media to give them their views on beauty, relationships, and standard of living. Thus, they seek out others that match society's views.

Shallowness is occasionally not genuine but an act performed by a person who is insecure or in need of attention.