au courant

1. Informed on current affairs; up-to-date.
2. Fully familiar; knowledgeable.

[French : au, in the + courant, current.]

adjective

Characteristic of recent times or informed of what is current: contemporary, current, mod, modern, up-to-date, up-to-the-minute. See knowledge/ignorance, new/old.

Definition: up to date
Antonyms: out of touch

The adjective has one meaning:

Meaning #1: being up to particular standard or level especially in being up to date in knowledge
  Synonyms: abreast of, au fait, up on