The dictionary provides us with basic definitions (usually near the bottom of the list): And, more helpfully, definitions of the opposites of "deep": Of course dictionary definitions are only the beginning, and most words can be subjected to over-analysis. Let's indulge in a bit of that here. How would you define depth and shallowness, in your own words (based on your own interactions)? Do you think they are correlated with certain functions (in Jungian and Myers-Briggs theory), or other personality traits like extroversion or introversion? Do you think depth and shallowness are necessarily good and bad, respectively, or do you think they have both pros and cons?