ни то ни сё

1) General subject: between hay and grass, betwixt and between, epicene creature, flesh nor fowl, grey area, neither fish, neither fish nor flesh, neither fish, flesh nor good red herring, nondescript, neither this nor that

2) Colloquial: half-and-halfer, whity-brown

3) Jargon: so-so, neither shit nor Shinola (from the proprietory name of a brand of shoe polish)

4) Set phrase: (used as pred.)(of persons) neither fish nor flesh, (used as pred.)(of persons)(of things) neither one thing nor another