15 entries under expression topic. ×
| limiting factor | |
| line of demarcation(idiom, border, borderline) | |
| back of beyond | |
| frontiers of knowledge | |
| matter of ignorance | |
| border area | |
| border zone | |
| boundary frontier | |
| dire straits(limit, edge, boundary) | |
| frontier zone | |
| leading edge | |
| outer limit(border, borderline) | |
| outlying border | |
| state line(noun, border, borderline) | |
| ultimate limit(limit, edge, boundary) |
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| APA | Smart Define. (2015). frontier thesaurus. Retrieved September 21, 2026, from https://smartdefine.org/frontier/thesaurus/synonyms |
| Chicago | Smart Define. 2015. "frontier thesaurus" https://smartdefine.org/frontier/thesaurus/synonyms (accessed September 21, 2026). |
| Harvard | Smart Define 2015, frontier thesaurus, Smart Define, viewed 21 September, 2026, <https://smartdefine.org/frontier/thesaurus/synonyms>. |
| MLA | Smart Define. "frontier thesaurus" 14 April 2015. Web. 21 September 2026. <https://smartdefine.org/frontier/thesaurus/synonyms> |