With verbs.

To some extent, in some degree (as intermediate between very or very much and not at all); moderately, tolerably, fairly; esp. indifferently well…

With expressed or implied limitation: only moderately; not above the average; slightly, indifferently, or poorly.

in a colourless manner; without colour.

= indifferently, adv. 5. Obsolete.

= passably, adv.

To a degree that is (just) acceptable; tolerably, adequately, moderately.

In a poor or sickly state of health; (also) in no particular manner or condition; without distinctive or orderly appearance or character. Also…

With only moderate prosperity, success, etc.

Colourlessly; in a monochrome or monochromatic way. Also in extended use.

Adequately or satisfactorily, rather than excellently, admirably, etc.; in a manner that is (just) good enough for the purpose.

So so, middling(ly).