A four letter word that starts with J and ends with M: jism.
methionylglutaminylarginyltyrosylglutamylseryllleucylpheny
A seven (7) letter word that starts with M and ends with O: memento
One very long word that starts with m is: microcryptocrystalline (22 letters)
The word is magnificent.
meander
major
matriarch, meaning female head of the family.
Actually, it starts and ends with "M", but you remove the first "M" and insert an "O" ANYWHERE in the word, not just replace "M" with "O"
Modernize is a word that starts with m and means to upgrade.
Make is a word that means to create and starts with "m".
Chum
Marvelous Or Modelesque (urban dictionary) Meaning having the look of a model.
Massasoit
my
mother, morning, modest, meaning, maize, mom, multiplication
Friend = mitram(N); sakhA(M) = comrade; snehitaH(M); vayasya = friend(of the same age);