What does "tonight" mean?

The nighttime of the current day or date; this night.

Tonight

Common synonyms include: this evening, as of now, as things are, at present, at this juncture, at this moment.

/təˈnaɪt/ adv, noun

adv, noun ·Uncommon ·College level

Noun

1
The nighttime of the current day or date; this night. uncountable, usually
"Tonight is the night."
2
the present or immediately coming night wordnet

Adverb

1
During the night following the current day; during the evening of today. not-comparable
"I want to party tonight!"
2
Last night. not-comparable, obsolete
"Besides, I met Lord Bigot and Lord Salisbury, With eyes as red as new-enkindled fire, And others more, going to seek the grave Of Arthur, whom they say is killed to-night On your suggestion."

Adverb

"We're going to eat a lot tonight so I hope you're not on a diet."

From Middle English tonyght, to niȝt, from Old English tō niht.