We found 8 dictionaries that define the word 1:

General (2 matching dictionaries)

1. -1: Dictionary.com
2. -1 (Mudvayne song), -1 (number), 1 (Beatles album), 1 (Demy album), 1 (Fischerspooner album), 1 (Julio Iglesias album), 1 (MBTA bus), 1 (New York City Subway service), 1 (Pole album), 1 (Suburban Kids with Biblical Names EP), 1 (The Beatles album), 1 (The Black Heart Procession album), 1 (The Motors album), 1 (Zara Larsson album), 1 (number), 1 (year): Wikipedia, the Free Encyclopedia

Art (1 matching dictionary)

3. Virginia Tech Multimedia Music Dictionary (No longer online)

Business (1 matching dictionary)

4. 1 (number): Legal dictionary

Computing (1 matching dictionary)

5. 1 (number), 1 (year): Encyclopedia

Miscellaneous (1 matching dictionary)

6. AbbreviationZ (No longer online)

Slang (1 matching dictionary)

7. The 1: Urban Dictionary

Tech (1 matching dictionary)

8. Rane Professional Audio Reference (No longer online)

(Note: See one as well.)

Definitions from WordNet (1) ▸ noun:  the smallest whole number or a numeral representing this number ▸ adjective:  used of a single unit or thing; not two or more Similar: skate over, rough sledding, puddle jumper, jump rope, ride shotgun, crash-dive, peel out, bottom out, ride herd on, wash out, more... Opposite: many, multiple, several, various, numerous Types: whole number, natural number, integer, rational number, real number, imaginary number, more... Phrases: s 1, m 1, l 1, g 1, h 1, more... ▸ Words similar to 1 ▸ Usage examples for 1 ▸ Idioms related to 1 ▸ Wikipedia articles (New!) ▸ Popular adjectives describing 1 ▸ Popular nouns described by 1 ▸ Words that often appear near 1 ▸ Rhymes of 1 ▸ Invented words related to 1