This word is acceptable for play in the US & UK dictionaries that are being used in the following games:

• Lexulous
• Wordscraper
• Wordosaur

v. To make less; reduce.

v. Archaic To make little of; belittle.

verb-intransitive. To become less; decrease. See Synonyms at decrease.

v. To make less; to diminish; to reduce.

v. To become less.

v. To make less; to reduce; to make smaller, or fewer; to diminish; to lower; to degrade

verb-intransitive. To become less; to shrink; to contract; to decrease; to be diminished

To become less; contract in bulk, quantity, number, or amount; decrease; diminish; shrink.

To come to appear less from increase of distance.

To make less; diminish; reduce in number, size, degree, or quality.

To degrade; reduce in dignity; depreciate; disparage.

To cause to appear less from increase of distance; specifically, in falconry, to soar above or beyond.

v. make smaller

v. wear off or die down

v. decrease in size, extent, or range

"If you have a Marine or Sailor in 1st platoon, don't be surprised if the frequency of your loved ones calls lessen and their e-mails stop altogether."

lessened    lessening    lessens   

weaken   

degrade    diminish    lower    abate    weaken    impair    decrease    reduce    shrink    contract   

Essen    caisson    cresson    delicatessen    lesson   

diminution    lower    escalation    heighten    weaken    widen    tighten    curtailment    cessation    loosen