1. One who has attained self-realization.
2. One who knows the Loka (cosmos) and Aloka (supra-cosmos).
'kṣetrajño' yathāvasthitātmasvarūpaparijñānādātmajña iti, athavā......lokālokasvarūpaparijñātetyarthaḥ.
(Sūtra 1.6.3 Vṛ Pa 143)
3. The person who knows the kṣetra, i.e., body, desire, sensory object, violence and the activities of mind, speech and body.
kṣetram- śarīram, kāmaḥ, indriyaviṣayaḥ, hiṃsā, manovākkāyapravṛttiśca. yaḥ puruṣaḥ etatsarvaṃ jānāti sa kṣetrajño bhavati.
(ĀBhā 316)
4. A knowledgable or a learned person.
jo dīhaloga- satthassa kheyaṇṇe, se asatthassa kheyaṇṇe.
(Ā 1.67)
...kṣetrajño-jñānī...
(ĀBhā 1.6 7)