A sunken, dispirited frame of mind.
A sunken, dispirited frame of mind — feeling cast down, and often prompted by circumstance.
Simple low spirits — the sense of being downcast or cast down — the most neutral and least freighted of this cluster (its literal root is “thrown down”). It lacks despondency's stress on lost heart and surrendered effort: one can be dejected without giving up. Far milder than despair (hope is not gone). It is an inner low mood, where gloom can also be a surrounding darkness; close to sadness but more plainly “downcast,” and less lingering or reflective than melancholy.
Early 15c. “degradation, humiliation”; c. 1500 “low spirits,” from Latin deicere “to cast down” (de- “down” + iacere “to throw”). The root image is “a throwing down.”
Narrowed from “degradation/humiliation” (early 15c.) to “low spirits” by c. 1500, now primary. Merriam-Webster notes the word (like melancholy and gloom) has been declining in use in favor of “depression” — a register cue that dejection now reads as slightly literary. No reliable recent-generation shift.