This word is acceptable for play in the US & UK dictionaries that are being used in the following games:

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n. Twilight; dusk.

n. twilight, as at early morning or (especially) early evening; dusk

n. sullenness; melancholy

n. Twilight; dusk; the fall of the evening.

n. Sullenness; melancholy.

n. The fall of the evening as the time of dusk or gloom; the twilight.

n. Hence—2. Closing period; decline: as, the gloaming of life.

n. 3. Gloominess of mood or disposition; glooming.

Of or pertaining to the gloaming or twilight.

n. the time of day immediately following sunset

"Also, part of the gloaming is the relative nascency of the EU itself."

daytime    nocturnal    nighttime    as    well    diurnal    darkness    daylight   

time of day    hour   

gloaming star   

gloom   

night   

twilight    dusk    sullenness    melancholy    dawn    vespers    sundown    crepuscule   

Wyoming    combing    foaming    homing    roaming   

greyness    half-light    brownness    refection    lunch-hour    hazes    stagnancy    grayness    Trilling    wilding