Those dictionary terms are not far off.
- subha: auspicious is better. That means it can mostly bring benefits.
- sukha : the opposite of dukha or suffering.
Tilakkhana (anicca, dukkha, anatta) are characteristics of nature. One could say asubha could/should be included there too. Of course, the word Tilakkhana is not in the Tipitaka; at least, I have not seen it in the Tipitaka.
- However, many suttas discuss only anicca, dukkha, anatta, and mutual relationships among them.
Asubha is always mentioned (together with anicca, dukkha, and anatta) under vipallasa (mental confusion.)