Function: intransitive verb
Date: circa 1535
1 : to enter something (as a building or computer system) without consent or by force
2 a : INTRUDE < break in upon his privacy> b : to interrupt a conversation
3 : to start in an activity or enterprise < breaking in as a cub reporter>
transitive verb
1 : to accustom to a certain activity or occurrence < break in the new clerk>
2 : to overcome the stiffness or newness of < break in a pair of shoes>