noun
falling on one's backside; pratfall
Almost always used in the phrase 尻餅をつく, meaning to fall and land on one's buttocks. The noun itself is rarely used independently.
See also: 尻餅をつく
凍った道で尻餅をついてしまった。
I slipped on the icy road and fell on my backside.
子供が遊んでいて尻餅を
The child fell on his bottom while playing.
noun
first-birthday mochi; mochi for making a baby fall
A traditional custom: a large mochi is tied to a baby's back on or before its first birthday, causing the baby to fall backward (尻餅をつく) as a ritual to ensure healthy growth. This sense is culturally specific and less common in daily conversation.
一歳の誕生日に、背中に尻餅を背負わせる風習がある。
There is a custom of tying a large mochi to a baby's back on its first birthday.
この地方では、尻餅を踏むことで子供の健やかな成長を願う。
In this region, they wish for the child's healthy growth by having it step on the first-birthday mochi.
General term for mochi rice cake. 尻餅 specifically refers to the ritual mochi for a baby's first birthday or the act of falling on one's backside.
Compound of 尻 (buttocks) and 餅 (mochi). The 'falling' sense comes from the resemblance of landing on one's bottom to a flattened mochi. The 'first-birthday mochi' sense is a literal use of the components.