This is a common acronym used in the Lego community - what does MOC mean?
MOC stands for "My Own Creation".
My Own Creation. Any LEGO creation designed and built by a LEGO fan without instructions. Generally pronounced “mock.”*
Found at this Lego glossary.
Brickipedia's version from their own glossary:
MOC - My Own Creation, a fan- made LEGO model
*A side note: There may be some LEGO fans who pronounce "MOC" the way the individual letters are pronounced - effectively saying "Em-Oh-See".
3You could note the grammatical conflict--I hear "a MOC" alot, given that people pronounce it as "MOCK," but I personally say "an MOC" and pronounce it "EM-OH-SEE."– PuragOct 29, 2011 at 7:08
Since when did the pronunciation of an acronym result in a grammatical conflict? May 6, 2018 at 4:27
A MOC or a Lego MOC, are the initials of My Own Creation, so, if you have made a creation or a Lego model out of your mind, I mean, with no instructions, you've made a MOC.