[GrammarPolice]

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CE - "timely" is an adverb describing the adjective "manner".

-Al

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"manner" is a noun.

Timely is both an adjective and an adverb, but its most common usage is as an adjective. Per American Heritage:

timely

SYLLABICATION: time·ly

ADJECTIVE: Inflected forms: time·li·er, time·li·est
1. Occurring at a suitable or opportune time; well-timed. 2. Archaic Coming too early; premature.

ADVERB: 1. In time; opportunely. 2. Archaic Early; soon.

As for the use of the second adjective: Coming too early, premature. One could say "Al ejaculated in a timely manner."