(geology) The time period with few coal deposits from the Permian to middle Jurassic.

(linguistics) A potential word, word sense, morpheme, or other form that does not exist in some language despite that it would be permissible by the grammatical rules of that language; its absence is therefore an accidental gap, in the ontologic sense of the word accidental (that is, circumstantial rather than essential).

Synonym of accidental gap

The strip of NATO-controlled territory along the Polish–Lithuanian border, separating Russia (Kaliningrad) from its ally Belarus.

(UK) Alternative form of gap fill.

plural of gap fill

plural of gap-fill

(UK) Synonym of fill in the blank.

The phenomenon that elements beyond fermium cannot be made by neutron bombardment, due to the very short spontaneous fission half-life of fermium-258.

simple past tense and past participle of stop-gap (alternative form of stopgapped)