crosswise; in a cross shape
Describes something arranged or moving in the shape of a cross, or two things intersecting at right angles.
彼は腕を十文字に組んで考え込んだ。
He folded his arms crosswise and thought deeply.
道が十文字に交差している。
The roads intersect crosswise.
From 十 (ten) and 文字 (character, letter), literally 'the character for ten', which is shaped like a cross. The adverbial form 十文字に means 'in a cross shape'.