unison
[noun]
Synonyms: agreement, accord, concert, concord, harmony, unity

[TahlilGaran] English Synonym Dictionary ▲

u‧ni‧son /ˈjuːnəsən, ˈjuːnɪsən, -zən/ noun
[Date: 1500-1600; Language: Old French; Origin: Medieval Latin unisonus 'having the same sound', from Latin uni- + sonus 'sound']
in unison
a) if people speak or do something in unison, they say the same words at the same time or do the same thing at the same time:
‘Good morning!’ the kids replied in unison.
b) if two groups, governments etc do something in unison, they do it together because they agree with each other:
Management and workers must act in unison to compete with foreign business.

[TahlilGaran] Dictionary of Contemporary English ▲