LEO:
sappy adj. (Amer.) [coll.] - albern, blöd, dämlich, kitschig, rührselig
sappy (Amer.) [coll.] adj. - trottelig auch: trottlig [ugs.] [pej.], vertrottelt
sappy adj. (Brit.) [coll.] - kitschig
sappy adj. [fig.] - kraftvoll, markig
sappy adj. - saftig
sappy adj. [fig.] - vital
sappy fracture - feinkörniger Bruch
sappy structure - feinkörniges Gefüge
Siehe Wörterbuch: sappy

Muret-Sanders, Oxford Duden
"sappy" hat (u.a.) drei Bedeutungen:
1. saftig
2. kraftvoll, markig, (full of vitality) voller Saft und Kraft
3. (coll.) einfältig, 'dämlich'
—MiMo, #4
Würde man also einen vitalen Rentner sappy nennen?
vital ist für mich rüstig, rege, gesund, lebensfroh
—Gine, #5
Siehe auch: vital - vital

Siehe auch: sappy - kitschig

NOAD (2001):
sappy - 1: [informal] oversentimental; mawkish.
2 (of a plant): containing a lot of sap.

AHD2 (1982, 1985):
sappy - 1. Full of sap; juicy. 2. [Slang.] Excessively sentimental; mawkish. 3. [Slang.] Silly or foolish.

Webster's 3rd unabridged (1961, 1981):
sappy - 1 a: abounding with sap b (dial): SUCCULENT, JUICY c (dial): becoming putrid: TAINTED d (dial): extremely damp: SODDEN e (of wool): having a superabundance of yolk f (of a feather): immature and with blood in the quill 2 a: resembling sapwood b: consisting largely of sapwood 3 a: foolishly or immaturely sentimental: MAWKISH b: lacking in good sense: FOOLISH, SILLY c: somewhat effeminate: FOPPISH 4 (chiefly Scot) a: fond of drinking b: cheerful as the result of drinking

Random House unabridged (1966):
sappy - 1. abounding in sap, as a plant. 2. full of vitality and energy. 3. [Slang.] silly or foolish.

OED:
sappy - 1. Of a plant or tree or its parts, of wood: Abounding in sap. ...
2. [fig.] in various applications. a. Full of vitality.
1558 ... 1879 ... A rank, sappy race like the English or German.
b. Full o[f] 'goodness' or substance.
1563 ... 1567 ... 1587 ... 1601 ... 1948 F. R. Leavis ... The Portrait of a Lady belongs to the sappiest phase of James's art, when the hypertrophy of technique hadn't yet set in.
†c. Immature, unseasoned. [Obs.] ...
†3. Juicy; succulent. a. Of fruit. Also as epithet of the juice. ...
b. Of meat, fish, etc. ...
4. Fat; plump. [Obs. exc. dial.] ...
5. a. Full of moisture; moist; wet; sodden; rainy. [Obs. exc. dial.] Cf. SOPPY a. ...
b. Of meat: Putrescent, tainted. [dial.] ...
6. Consisting of or containing sap-wood. ...
7. Foolish. (Cf. SAP sb.^5.) ...

This sense no longer appears in the more recent dictionaries, at least in AE.

I just wondered if anyone was still familiar with it and could turn up an example from a reliable print source later than 1948. (For example, in OED online?)

If not, I suggest it be marked obsolete.

I'm also wondering if the [Amer.] and [Brit.] senses are really still that different; they seem to overlap to some degree.