From WordNet (r) 2.0 (August 2003) [wn]:
tonight
n : the present or immediately coming night
adv : during the night of the present day; "drop by tonight" [syn:
this evening, this night]
From The Collaborative International Dictionary of English v.0.48 [gcide]:
Tonight \To*night"\, adv. [Prep. to + night]
1. On this present or coming night.
[1913 Webster]
2. On the last night past. [Obs.] --Shak.
[1913 Webster]
From The Collaborative International Dictionary of English v.0.48 [gcide]:
Tonight \To*night"\, n.
The present or the coming night; the night after the present
day.
[1913 Webster]