eclipse period; eclipse phase
Virology term for the stage in a viral lifecycle after entry into a host cell when no complete virions are detectable.
After entering the host cell, the virus enters the eclipse period.
Metaphorical use for a period of stagnation, decline, or obscurity, often in historical or cultural contexts.
That civilization experienced a dark age lasting several centuries.
Compound of 暗黒 (darkness) and 期 (period). The virology sense is a calque of English 'eclipse period'.