playing with dirt; making things out of dirt for fun
Refers to children's play involving soil, mud, or sand, often with a creative or exploratory aspect.
When I was a child, I used to play with dirt a lot.
In the garden after the rain, the children are absorbed in playing with the mud.
Standard kanji spelling.
Mixed kanji-kana spelling, common in children's contexts or when the kanji 遊 is considered difficult.
Compound of 土 (tsuchi, 'earth, soil') and 遊び (asobi, 'play'). The exact historical derivation is uncertain, but the word is transparently formed from these elements.