Top Definition
To show no interest or concern for an activity.

The opposite of the phrase 'keen as mustard'.

The phrase is believed to come from the fact that mayonaise is the opposite to mustard. They are both condiments but mayo is to an egg what mustard is to a seed.
Person 1: Have you written much of your essay?
Person 2: Nope, I'm about as keen as mayo, all I've done is plagiarise 2,000 words.
by DennisCarbon August 25, 2011
Free Daily Email

Type your email address below to get our free Urban Word of the Day every morning!

Emails are sent from We'll never spam you.