We don't have synonyms for highten yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are tighten, heighten and lighten.
°To carry forward; to advance; to increase; to augment; to aggravate; to intensify; to render more conspicuous; -- used of things, good or bad; as, to heighten beauty; to heighten a flavor or a tint.
°To carry forward; to advance; to increase; to augment; to aggravate; to intensify; to render more conspicuous; -- used of things, good or bad; as, to heighten beauty; to heighten a flavor or a tint.