A fluid delivery device for discharging a fluid comprising: a housing; a piston pump; a biasing mechanism; and a trigger mechanism; the housing comprising a basal end and a discharge end having an outlet for discharging the fluid; the piston pump comprising a casing defining a pump chamber for storage of the fluid, a piston slidably movable relative to the pump chamber, a piston plunger, and a delivery channel for delivering fluid discharged from the pump chamber to the outlet of the housing; the trigger mechanism being movable from a cocked configuration to a triggered configuration; in the cocked configuration the trigger mechanism prevents transfer of a biasing force of the biasing mechanism to the casing to thereby prevent movement of the casing towards the outlet of the housing; in the triggered configuration the trigger mechanism enables transfer of the biasing force to the casing to thereby cause movement of the casing towards the outlet of the housing so as to discharge fluid from the pump chamber, along the delivery channel and out of the outlet of the housing; the biasing mechanism comprising one or more flexible catch members which in the cocked configuration are catched to the housing and in the triggered configuration are decoupled from the housing; and wherein the trigger mechanism comprises a manually operable trigger located at the basal end of the housing, the manually operable trigger comprising a shroud and a slidable button being slidable relative to the shroud; the slidable button comprising an obstructer that in the cocked configuration engages the one or more flexible catch members to prevent decoupling of the one or more catch members from the housing; wherein in the cocked configuration the slidable button projects outside the shroud so as to be accessible, and wherein in the triggered configuration the slidable button is retained within the shroud to provide a visual and tactile activation indicator. a housing; a piston pump; a biasing mechanism; and a trigger mechanism; the housing comprising a basal end and a discharge end having an outlet for discharging the fluid; the piston pump comprising a casing defining a pump chamber for storage of the fluid, a piston slidably movable relative to the pump chamber, a piston plunger, and a delivery channel for delivering fluid discharged from the pump chamber to the outlet of the housing; the trigger mechanism being movable from a cocked configuration to a triggered configuration; in the cocked configuration the trigger mechanism prevents transfer of a biasing force of the biasing mechanism to the casing to thereby prevent movement of the casing towards the outlet of the housing; in the triggered configuration the trigger mechanism enables transfer of the biasing force to the casing to thereby cause movement of the casing towards the outlet of the housing so as to discharge fluid from the pump chamber, along the delivery channel and out of the outlet of the housing; the biasing mechanism comprising one or more flexible catch members which in the cocked configuration are catched to the housing and in the triggered configuration are decoupled from the housing; and the biasing mechanism comprising one or more flexible catch members which in the cocked configuration are catched to the housing and in the triggered configuration are decoupled from the housing; and wherein the trigger mechanism comprises a manually operable trigger located at the basal end of the housing, the manually operable trigger comprising a shroud and a slidable button being slidable relative to the shroud; the slidable button comprising an obstructer that in the cocked configuration engages the one or more flexible catch members to prevent decoupling of the one or more catch members from the housing; wherein in the cocked configuration the slidable button projects outside the shroud so as to be accessible, and wherein in the triggered configuration the slidable button is retained within the shroud to provide a visual and tactile activation indicator.