At the same instant/moment, abreast, (all) together, and at one and the same time are all synonyms for side by side. In line, apart, and separately are these antonyms of side by side. And here are another 16 synonyms for side by side.
Side by side Synonyms
1. abreast
- Abreast
- Alongside (each other)
- Beside each other
- Cheek by jowl
- Level
- Shoulder to shoulder
- Together
- Close together
2. simultaneously
- (all) together
- At one and the same time
- At the same instant/moment
- At the same time
- Contemporaneously
- Simultaneously
- As a group