"Trochaic" refers to the existence of "trochees," or "trochaic feet." A trochee is a long syllable, or stressed syllable, followed by a short, or unstressed, one. In the case of "razor," the emphasis is in the syllable "RA-," while "-zor" is unstressed. This is in contrast with iambic words, which are more common in English. Because of this, poems and other texts that use trochaic meters often sound unnatural to the ear.
The word razor is trochaic because it consists of Ra - zor in which ra is accented and pronounced the clearest and loudest. If zor was accented then it would be iambic.
