In its most literal sense the term means sexual attraction to statues. This may also be extended to mannequins and/or dolls.
In a broader sense the term may refer to sexual fantasies about oneself and/or others being transformed into, or simply rendered as motionless as, a statue, mannequin or doll. Such fantasies may of course be extended to roleplaying.
There is a broad crossover between agalmatophilia and robot fetishism or ASFR (alt.sex.fetish.robots).