British Person
Brit
noun
イギリス means "Great Britain" or "United Kingdom." So what is a "Great Britain person?" You guessed it — a British person, or Brit.
Often times, when two kanji come together to form a kanji compound (or jukugo), you use the on'yomi readings. This is similar to that, though instead of another kanji it's a foreign word. This pattern works with almost any country as well. Just add 人 to a country name and you've described the people who live there. You'll see more of these before you're finished here.
And since 人 has two on'yomi readings, here's a mnemonic to help you remember which one to use:
As with all words for nationalities, the 人 here is pronounced じん. All nationalities, including Brits, love jeans (じん)!
ジェニーさんはイギリス人です。
Jenny is British.
この本は、イギリス人とアメリカ人のチームがつくりました。
This book was created by a team of Brits and Americans.
そりゃ、イギリス人もコーヒーをのみますよ。
Well, British people also drink coffee.