light-tight

• lighttight

From light (noun) +‎ tight (adjective).

• enPR: lītʹtīt

light-tight (comparative more light-tight, superlative most light-tight)

1. Impervious to light; excluding the light perfectly.
   • 2000, Stephen G. Anchell, The darkroom cookbook, page 127:

     From a practical point of view it is not always possible to achieve an absolute lighttight home darkroom.

• lightproof

• For other similar compound words, see the derived terms under tight.

William Dwight Whitney and Benjamin E[li] Smith, editors (1914), “light-tight”, in The Century Dictionary: An Encyclopedic Lexicon of the English Language, revised edition, volumes III (Hoop–O), New York, N.Y.: The Century Co., →OCLC, page 3450.