We found 22 dictionaries that define the word tree line:

General (16 matching dictionaries)

1. tree line: Longman Dictionary of Contemporary English
2. tree line: American Heritage Dictionary of the English Language
3. tree line: Collins English Dictionary
4. tree line: Vocabulary.com
5. tree-line: Wordnik
6. tree-line, tree line: Wiktionary
7. tree line: The Wordsmyth English Dictionary-Thesaurus
8. tree line: Infoplease Dictionary
9. tree line: Dictionary.com
10. Tree line: Wikipedia, the Free Encyclopedia
11. tree line: Rhymezone
12. tree line: FreeDictionary.org
13. tree line: Mnemonic Dictionary
14. tree line: TheFreeDictionary.com
15. tree line: Merriam-Webster
16. tree line: Oxford Learner's Dictionaries

Business (1 matching dictionary)

17. Travel Industry Dictionary (No longer online)

Computing (1 matching dictionary)

18. Tree-line, tree line: Encyclopedia

Science (2 matching dictionaries)

19. Archaeology Wordsmith (No longer online)
20. Botanical Terms (No longer online)

Tech (2 matching dictionaries)

21. Glossary of Meteorology (No longer online)
22. Lake and Water Word Glossary (No longer online)

(Note: See tree_lines as well.)

Definitions from Wiktionary (tree line) ▸ noun:  A division in altitude (or latitude) above which trees tend not to grow on mountains. Similar: timber line, timberline, treeline, tree-line, fog line, line, range, isabnormal, drip line, ridge, more... Opposite: treeline-free, timberline-free, alpine zone-free Phrases: Family tree of Confucius in the main line of descent, more... Adjectives: riverward, brim, upcountry, underfloor, offshore, side, landward, shoreward, landlocked, inshore, rand ▸ Words similar to tree line ▸ Usage examples for tree line ▸ Idioms related to tree line ▸ Wikipedia articles (New!) ▸ Words that often appear near tree line ▸ Rhymes of tree line ▸ Invented words related to tree line