The word “stay” most closely means the following as it is used in line 39: Stop or pause.
What is the meaning?
The line is part of a passage describing the curse placed upon the Lady of Shalott. The curse states that if she looks down at Camelot, "a curse is on her if she stay." This implies that "stay" refers to continuing to look or remaining focused on the world outside her tower.
The Lady's confinement and desire for the outside world are central themes in the poem. By interpreting "stay" as stop or pause, we maintain the contrast between her restricted existence and the alluring possibilities beyond her window.