Virtually means almost — so nearly that the gap stops mattering. The town was virtually empty by nine, the tickets are virtually sold out, it is virtually impossible to park here on a Saturday.
It stands in front of the word it softens and it prefers absolutes: virtually identical, virtually every, virtually nothing, virtually impossible. Virtually empty admits that somebody is still in there, so the word is a way of being accurate rather than a way of exaggerating. The second meaning came in with computers: to meet virtually, work virtually or tour a museum virtually is to do it through a screen instead of in person. The two senses live far enough apart that the sentence tells you which one you have. Do not mix it with virtuously, which means in a morally good way — one letter, and a very different meeting.
1adverbvirtuallyAlmost entirely; in every way that matters.
“The building was virtually finished by the time the money ran out.”
synonyms: practically, nearly
2adverbmeansBy means of a computer or a network, rather than in person.
“The whole team now meets virtually on Monday mornings.”
Also accepted in games: practically
Virtually is virtual plus -ly, and Middle English already had it as vertually — six hundred years before anyone attended a meeting through a laptop. The old sense of virtual was 'in effect, if not in name', which is why virtually still means 'as good as'. The computer meaning is the newcomer, riding on a very old word.
Middle English
vertually
English, today
virtually
From Middle English vertually; equivalent to virtual + -ly.
Etymology from Wiktionary, CC BY-SA