imperceptible (adjective) imperceptible: hard to sense; faint
Sinonime: dejected, depressed, despondent, disconsolate,
dismal, dispirited, down in the dumps, downcast, downhearted,
fed up*,
gloomy,
glum, low,
melancholy,
moody,
unhappy, woebegone
Antonime: gay, happy,
joyful,
joyous,
lighthearted,
upbeat