Mobile, a.
Etymology: [L. mobilis, for movibilis, fr. movere to move: cf. F. mobile. See Move.]
1. Capable of being moved; not fixed in place or condition; movable. "Fixed or else mobile." Skelton.
2. Characterized by an extreme degree of fluidity; moving or flowing with great freedom; as, benzine and mercury are mobile liquids; -- opposed to viscous, viscoidal, or oily.
3. Easily moved in feeling, purpose, or direction; excitable; changeable; fickle. Testament of Love. The quick and mobile curiosity of her disposition. Hawthorne.
4. Changing in appearance and expression under the influence of the mind; as, mobile features.
2 more senses
5. (Physiol.)
Capable of being moved, aroused, or excited; capable of spontaneous movement.
1 other Webster entry under this spelling
Mobile, n.
The mob; the populace. [Obs.] "The unthinking mobile." South.
Shades of meaning
Fernald has no entry of its own for mobile; he lists it under active.
He lists it without comment; the entries above explain its neighbors.