ぞくぞく

Etymology 1
From reduplication of, itself from.

Adjective

 * 1)   grouped together, bunched up

Usage notes
Used with the adverbial particle.

More commonly read as.

Etymology 2
From reduplication of ideophonic element, also found in of similar meaning.

Pronunciation
A surface analysis suggests ideophonic expressing a sense of "buzz" or "shiver", appended with ideophonic  possibly expressing a sudden change in state.

Likely cognate with the zo element in, ,.

Adverb

 * 1) shiveringly, with a shudder

Usage notes
May be used with the adverbial particle.

Verb

 * 1) to shiver, to feel a chill, as from cold or fear
 * 2) to be vibrating as from joy or excitement
 * 3) to shudder from fear, to have the creeps
 * 1) to shudder from fear, to have the creeps

Usage notes
Zokuzoku implies an ongoing shiver, whereas synonyms zokutto and zotto imply a one-time shiver.

Etymology 3
From reduplication of, itself from.

Adverb

 * 1)  successively, one after another

Usage notes
Used with the adverbial particle.