Mediate, v. i. [imp. & p. p. Mediated; p. pr. & vb. n. Mediating.]
Etymology: [LL. mediatus, p. p. of mediare to mediate. See Mediate, a.]
1. To be in the middle, or between two; to intervene. [R.]
2. To interpose between parties, as the equal friend of each, esp. for the purpose of effecting a reconciliation or agreement; as, to mediate between nations.
2 other Webster entries under this spelling
Mediate, a.
1. Being between the two extremes; middle; interposed; intervening; intermediate. Prior.
2. Acting by means, or by an intervening cause or instrument; not direct or immediate; acting or suffering through an intervening agent or condition.
3. Gained or effected by a medium or condition. Bacon. An act of mediate knowledge is complex. Sir W. Hamilton.
Mediate, v. t.
1. To effect by mediation or interposition; to bring about as a mediator, instrument, or means; as, to mediate a peace.
2. To divide into two equal parts. [R.] Holder.
Shades of meaning
Fernald has no entry of its own for mediate; he lists it under interpose.
He lists it without comment; the entries above explain its neighbors.