1 additional, added, auxiliary, accessory, supplementary, supplemental, further, ancillary, subsidiary, collateral, adventitious:
We had an extra person for dinner. Zenobia has an extra toe on each foot.
2 leftover, excess, spare, surplus, unused, superfluous, supernumerary, reserve:
After all were served, we had two extra desserts.
3 addition, addendum, accessory, appurtenance, supplement, bonus, premium, dividend:
As an extra, each customer receives a free ball-point pen.
4 supplement, US mark-up, surcharge, Slang US and Canadian kicker:
There is an extra if you want bread and butter.
5 supernumerary, walk-on, Colloq super, spear-carrier:
One could scarcely call being an extra a 'Hollywood career'.
6 uncommonly, unusually, exceptionally, unexpectedly, extraordinarily, remarkably, notably, surprisingly, amazingly, very, particularly, especially, extremely, strikingly:
Teacher said that Philip was extra good today.
7 additionally, again, more, in addition:
They charge extra for room service.