Fast
Fast adjective - Firm in one's allegiance to someone or something.
Usage example: the two girls soon became fast and inseparable friends
Treacherous is an antonym for fast.
Treacherous
Treacherous adjective - Not true in one's allegiance to someone or something.
Usage example: a treacherous “friend,” she's been known to turn against people in the blink of an eye
Fast is an antonym for treacherous.
Nearby Words: treachery, treacherously
Both words in one sentence
- Names to Run Away from Really Fast: Subverted with Judas Porcius, who's friendly and not treacherous at all, although like the Biblical Judas he does commit suicide.
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Unlike most identities on this page, the harsh world and simultaneously squishy and treacherous nature of gretchin mean that the turnover is so fast you randomly determine the Red Gobbo's stats at the beginning of each game.
Source: Legacy Character
Cite this Source
Treacherous and Fast. (2016). Retrieved 2026, July 21, from https://thesaurus.plus/related/fast/treacherous
Fast & Treacherous. N.p., 2016. Web. 21 Jul. 2026. <https://thesaurus.plus/related/fast/treacherous>.
Treacherous or Fast. 2016. Accessed July 21, 2026. https://thesaurus.plus/related/fast/treacherous.
Google Ngram Viewer shows how "fast" and "treacherous" have occurred on timeline