CU

Noun

• Initialism of credit union
• Initialism of control unit
• Initialism of close-up

Proper Noun

• Christian Union (bodies of Christian students in UK schools, colleges and universities)
• Chittagong University in Bangladesh
• Chulalongkorn University in Thailand

Adjective

• cubic in a variety of English customary units (examples: cubic inch, cubic foot).

Phrase

• in stamp descriptions, commercially used.
• phonetic abbreviation of see you.