toastmaster
dreadnought
Except you gave us 11 letters that spell "celebrating."
Feud is a four letter word. The Official Scrabble Dictionary includes the word yeuk. It means to itch. It has a scrabble value of 11 points.
delivery man
Only one I can think of is Solid Disk Drive but it's 16 letters not 11
There are 11 letters in the word mathematics. 2 of those 11 are A's. Probability is therefore 2/11.
The letters can be used to spell the 11 letter word nonathletic. They also spell the 9 letter word attention.
Rameshwaram
An 11 letter word that means "to invade someone's privacy" is "trespassing".
The Official Scrabble Players Dictionary includes the 7 letter word chosen. It is a valid scrabble word that means to take by preference. The word has a scrabble point value of 11 points.
The eleven letter word is preliminary.
There is no English 11-letter word you can make using all of the letters in accomplish and adding one more letter.