They may feel tired, and though outwardly calm, can be irritable.

他们可能觉得累，所以尽管表面上平静，却可能容易发怒。

《柯林斯英汉双解大词典》

When people grow old, sometimes they turn to be irritable and stubborn.

当人们变老。有时他们就会变得暴躁而又顽固。

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If your blood sugar level is low, you're going to find it hard to concentrate, and you might well be irritable and moody.

如果你的血糖低，你会发现很难集中精力，你会变得过敏的和喜怒无常的。

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The early signs of ovarian cancer can be confused with irritable bowel syndrome (IBS).

BBC: Ovary cancer signs 'confusion'

McCain can be combative and irritable in his town-hall meetings.

NEWYORKER: On the Bus

Similarly, a former college athlete who becomes angry and irritable in his 40s could be suffering a midlife crisis or delayed reaction to head injuries sustained decades earlier.

WSJ: Confusing Medical Ailments With Mental Illness