The thickest, or most active or intense, part of something.
"The storm's violence hit its thick during the night when winds howled and rain lashed against the windows."
In plain English: A thick person is someone who is slow to learn or understand things.
"The soup was too thick to pour."
To thicken.
"The chef stirred the sauce until it began to thicken into a rich gravy."
In plain English: To make something thicker by adding more of it.
"The fog began to thicken just as we reached the edge of the forest."
not thin; of a specific thickness or of relatively great extent from one surface to the opposite usually in the smallest of the three solid dimensions
"an inch thick"
"a thick board"
"a thick sandwich"
"spread a thick layer of butter"
"thick coating of dust"
"thick warm blankets"
having component parts closely crowded together
"a compact shopping center"
"a dense population"
"thick crowds"
"a thick forest"
"thick hair"
(used informally) associated on close terms
"a close friend"
"the bartender was chummy with the regular customers"
"the two were thick as thieves for months"
(used informally) stupid
"That thick kid missed the joke again."
Relatively great in extent from one surface to the opposite in its smallest solid dimension.
"The book is so thick that I haven't even reached the halfway point yet."
In plain English: Thick means having a large distance from one side to the other, like a chunky piece of bread or dense fog.
Usage: Use thick to describe objects with substantial depth or density, such as walls of ice or heavy fabrics. Avoid confusing it with deep when referring specifically to vertical distance below a surface level.
In a thick manner.
"The crowd was so thick that we couldn't even see each other's faces through the throng."
In plain English: Thick means doing something with great effort and intensity.
"The fog was so thick we couldn't see more than a few feet ahead."
The word thick comes from the Old English þicce, meaning "thick" or "dense." It traveled into Middle English as thikke and has retained its original sense ever since.