C.O. /ˌsiː ˈəʊ◂ $ -ˈoʊ◂/ noun [countable]
(Commanding Officer) an officer who is in charge of a military unit

[TahlilGaran] Dictionary of Contemporary English ▲

CO
written abbreviation for Colorado

[TahlilGaran] Dictionary of Contemporary English ▲

co- /kəʊ $ koʊ/ prefix
[Language: Latin; Origin: 'together, with', from com-; ⇒ COM-]

1. together with:
to coexist (=exist together or at the same time)
coeducation (=with boys and girls together)

2. doing something with someone else as an equal or with less responsibility:
my co-author (=someone who wrote the book with me)
the co-pilot (=someone who helps a pilot)

[TahlilGaran] Dictionary of Contemporary English ▲

Co. /kəʊ $ koʊ/

1. the abbreviation of company:
James Smith & Co.

2. and co British English spoken the other members of a particular group of people:
I can’t say I’m looking forward to seeing Angela and co again.

3. the written abbreviation of county:
Co. Durham

[TahlilGaran] Dictionary of Contemporary English ▲

CO
Carbon Monoxide 
Central Office (telecommunications/telephony) 
Chill Out 
Colorado 
Commanding Officer 
Company

[TahlilGaran] Acronyms and Abbreviations Dictionary ▲