~と adverb / adverb:

• lapping (e.g. of waves against the shore) - onomatopoeia
• steadily (advancing); gradually (approaching) - onomatopoeia

~の noun / adjectival noun:

• sufficient (of the amount of liquid needed to cover a submerged object); just enough - often used adverbially as ひたひたに - onomatopoeia

~と adverb / adverb:

• speedily; promptly; quickly; smoothly - onomatopoeia - archaism
• closely; exactly - onomatopoeia - archaism