It looks like heat damage or sunburn. Did it get close to a window? This is a Phalaenopsis orchid. They do best with bright shade and no direct sunshine.
There is a great thread on Orchid Board about growing Phalaenopsis. From the left menu select Forums, then Beginners Forum, then look at the sticky thread near the top, The Phal Abuse Stops Here. Also look at the thread about using wooden cooking skewers to determine when to water.
__________________ May the bridges I've burned light my way.
I agree that looks like sunburn damage. That leaf tip was probably exposed to bright sunlight that hit it more directly than any other part of the plant because of the change in angle of exposure due to curve of the leaf. It is mostly dry and not spreading anymore it is nothing to worry about, except to make sure it doesn't happen again.