1 a : a distance below a surface [count] ▪ These fish typically live at depths of 500 feet or more. ▪ Students will test the temperature of the water at different/varying/various depths. ▪ shallow/great depths ▪ The boat sank to a depth of several hundred feet. ▪ measuring the depth of the water/river/sea ▪ the depth of a hole ▪ The pool has a depth of 12 feet. [noncount] ▪ The pool is 12 feet in depth. [=12 feet deep]
b [count] : the distance from the front of something to the back — usually singular ▪ Measure the height, width, and depth of the cabinet. ▪ The bench's depth is 22 inches. 2 [count] : an area that exists far below a surface or far inside something : a deep place or area — usually plural ▪ They disappeared into the depths of the forest. ▪ Scientists have begun using the machine to explore the ocean depths. ▪ the black depths of outer space — often used figuratively ▪ The actress must examine her own emotional depths to perform the role successfully. ▪ Around midnight, a loud noise woke us from the depths of sleep. ▪ I knew in the depths of my heart/soul/being [=I believed very strongly] that we would survive. ▪ The memory lies hidden in the depths of her mind. [=she has not thought about the memory in a long time] ▪ in the depths of winter [=in the middle of winter; in the coldest part of winter] 3 [count] a : a very low or bad state or condition — usually plural ▪ After losing his job, he sank into the depths of misery/despair/depression. ▪ The film portrays a family's difficult climb from the depths of poverty. ▪ I can't believe he lied. He's really sunk to new depths. ▪ The team is reaching/plumbing new depths this season. [=the team is playing worse than it ever has before]
b : the worst part of something
▪ I began working at the factory during the depth/depths of the Depression. 4 [noncount] : the quality of being deep: such as a : the quality of being strongly felt
▪ We were surprised by the depth of her anger/pain/shame. ▪ He wanted to express the depth of his love for her. ▪ No one doubted the depth of his faith. [=they all knew that his faith was strong] ▪ the depth of her commitment to the project ▪ The dancers expressed great depth of feeling/emotion.
b : the quality of being very bad or serious
▪ I was shocked when I realized the depth of the problem.
c : the quality of being complete or thorough
▪ We were impressed by the depth [=extent] of her experience/knowledge. ▪ Your essay lacks depth. [=it does not cover its topic in a complete way]
d : the quality of being strong in color, taste, etc.
▪ the depth of a color ▪ The wine has great depth of flavor.
e : the quality of being low in sound
▪ the depth of his voice
f US, sports : the quality of having many good players on a team
▪ The team lacks depth this year.