SING

• sing past tense sang, past participle sung
• 1

  with your voice

   [intransitive and transitive] to produce a musical sound with your voice:
• She can sing beautifully.
• Most children enjoy singing.
• We had a great time singing some of the old songs.
• sing to
• My mother used to sing to me when I was young.
• He was singing to himself quietly.
• sing somebody something
• Come on, sing us a song!
• I've never been able to sing in tune (=sing the correct notes).
• She patiently sang the baby to sleep.
• ➔ singing
• 2

  birds

   [intransitive] if birds sing, they produce high musical sounds:
• I could hear the birds singing outside my window.
• 3

  high noise

   [intransitive always + adverb/preposition] to make a high whistling sound:
• A kettle was singing on the stove.
• sing past
• A bullet sang past my ear.
• 4

   sing somebody's praises

  to praise someone very much:
• Mrs Edwards was singing your praises today.
• 5

   sing a different tune

  to say something different from what you said before:
• You're singing a different tune now!
• 6

   be singing from the same hymn sheet/book

  used to say that a group of people all have the same aims or all express the same opinion on a particular subject:
• Union representatives are all singing from the same hymn sheet on the issue of pay.
• 7

  give information

   [intransitive] informal to tell people everything you know about a crime when they ask you questions about it - used especially by criminals and the police:
• I think he'll sing.

• sing along 

  phrasal verb
• to sing with someone else who is already singing:
• Sing along if you know the words.
• sing along to
• Jess was singing along to the radio.

• sing out 

  phrasal verb
• 1

   sing out (something)

  to shout or sing some words clearly and loudly:
• 'Freeze!' a shrill voice sang out.
• 2 American English to sing loudly so that people can hear you easily

• sing up 

  phrasal verb
• to sing more loudly:
• Sing up, boys, I can't hear you!

Definition from the Longman Dictionary of Contemporary English
Advanced Learner's Dictionary.