From weak +‎ -en.

• (US) IPA^(key): /ˈwikən/

• Audio (Southern England):

  (file)

• Rhymes: -iːkən

weaken (third-person singular simple present weakens, present participle weakening, simple past and past participle weakened)

1. (transitive) To make weaker or less strong.

   Synonym: emasculate (literary)

   weaken a bond

   weaken a joint

2. (intransitive) To become weaker or less strong.

   Over the years my enthusiasm for the job has weakened.

   • 1958, President Dwight Eisenhower, 3:06 from the start, in President Eisenhower Speaks On The Formosa Situation (1958)‎^[1], British Pathé:

     My friends, we are confronted with a serious situation. But it is typical of the security problems of the world today. Powerful and aggressive forces are constantly probing, now here, now there, to see whether the free world is weakened. In the face of this, there are no easy choices available. It is misleading for anyone to imply that there are. However, the present situation, though serious, is by no means desperate or hopeless.

• weaken up