Question: words are hard to say?
Answer: 10 - Rural. Submitted by user 'mattythedog', rural appears to cause problem particularly when repeated or put next a word with similar “r” sounds. ... 
9 - Otorhinolaryngologist. ... 
8 - Colonel. ... 
5 - Isthmus. ... 
4 – Anemone. ... 
3 - Squirrel. ... 
2 – Choir. ... 
1 – Worcestershire.