Insignificantly small; a matter of form. "For a nominal fee." Except when it comes to NASA which, being engineers, they made up their own meaning for the word, which seems to be "normal", but they don't want to say a flight is normal because then they'd have to say "not normal" when some fudge didn't work, for which they have some other terms to obfuscate their boo-boos. My guess, YMMV.

Nom"i*nal (?), a. [L. nominalis, fr. nomen, nominis, name. See Name.]

1.

Of or pertaining to a name or names; having to do with the literal meaning of a word; verbal; as, a nominal definition.

Bp. Pearson.

2.

Existing in name only; not real; as, a nominal difference.

Macaulay.

© Webster 1913.

Nom"i*nal, n.

1.

A nominalist.

Camden.

2. Gram.

A verb formed from a noun.

3.

A name; an appellation.

A is the nominal of the sixth note in the natural diatonic scale. Moore (Encyc. of Music. )

© Webster 1913.