vexatious

日本で増え続ける外来種の動物たちが問題となっています。
Alien invasion: Vexatious foreign species are increasingly taking up residence in Japan

Shibuya has a rat problem.

The rodents are lured to the area by the promise of an abundant supply of food scraps, which sit in the kitchens of countless restaurants and bars scattered throughout the capital’s famous shopping and entertainment district.

On some days of the week, the waste is even collected, placed into flimsy plastic bags and left in piles on the side of a road — with nobody guarding it. As far as rats are probably concerned, Shibuya is a rodent’s paradise.
http://www.japantimes.co.jp/life/2015/12/05/environment/space-invaders-vexatious-foreign-species-increasingly-taking-residence-japan/#.VmnXFTihdMs

今回取り上げる表現は見出しの “vexatious”です。『ジーニアス英和辞典第4版（大修館書店）』では「〘やや古〙いらだたしい、腹立たしい；面倒な、厄介な」と書かれていました。LDOCEでは “making you feel annoyed or worried”と定義されていました。

この表現は“vex”の派生語です。 “vex”はラテン語vexare（感情などをかき乱す、苦しめる）からきています。(Inaho)